While looking into the performance of scrub I noticed that a significant
amount of time is being used for loading the extent tree and the csum
tree. While this is no surprise I did some prototyping on how to improve
on it.
The main idea is to load the tree (or parts of it) top-down, order the
needed blocks and distribute it over all disks.
To keep you interested, some results first.
a) by tree enumeration with reada=2
reading extent tree: 242s
reading csum tree: 140s
reading both trees: 324s
b) prefetch prototype
reading extent tree: 23.5s
reading csum tree: 20.4s
reading both trees: 25.7s
The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled
28%. It is created with the current git tree + the round robin patch and
filled with
fs_mark -D 512 -t 16 -n 4096 -F -S0
The ''normal'' read is done by enumerating the leaves by
btrfs_next_leaf()
with path->reada=2. Both trees are being enumerated one after the other.
The prototype currently just uses raw bios, does not make use of the
page cache and does not enter the read pages into the cache. This will
probably add some overhead. It also does not check the crcs.
While it is very promising to implement it for scrub, I think a more
general interface which can be used for every enumeration would be
beneficial. Use cases that come to mind are rebalance, reflink, deletion
of large files, listing of large directories etc..
I''d imagine an interface along the lines of
int btrfs_readahead_init(struct btrfs_reada_ctx *reada);
int btrfs_readahead_add(struct btrfs_root *root,
struct btrfs_key *start,
struct btrfs_key *end,
struct btrfs_reada_ctx *reada);
void btrfs_readahead_wait(struct btrfs_reada_ctx *reada);
to trigger the readahead of parts of a tree. Multiple readahead
requests can be given before waiting. This would enable the very
beneficial folding seen above for ''reading both trees''.
Also it would be possible to add a cascading readahead, where the
content of leaves would trigger readaheads in other trees, maybe by
giving a callback for the decisions what to read instead of the fixed
start/end range.
For the implementation I''d need an interface which I haven''t
been able
to find yet. Currently I can trigger the read of several pages / tree
blocks and wait for the completion of each of them. What I''d need would
be an interface that gives me a callback on each completion or a waiting
function that wakes up on each completion with the information which
pages just completed.
One way to achieve this would be to add a hook, but I gladly take any
implementation hints.
--
Arne
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs"
in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
On 23.03.2011 14:06, Arne Jansen wrote:> While looking into the performance of scrub I noticed that a significant > amount of time is being used for loading the extent tree and the csum > tree. While this is no surprise I did some prototyping on how to improve > on it. > The main idea is to load the tree (or parts of it) top-down, order the > needed blocks and distribute it over all disks. > To keep you interested, some results first. > > a) by tree enumeration with reada=2 > reading extent tree: 242s > reading csum tree: 140s> reading both trees: 324ssorry, the number is wrong, it should be 384s (just the sum of both ./. rounding errors).> > b) prefetch prototype > reading extent tree: 23.5s > reading csum tree: 20.4s > reading both trees: 25.7s > > The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled > 28%. It is created with the current git tree + the round robin patch and > filled with > > fs_mark -D 512 -t 16 -n 4096 -F -S0 > > The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() > with path->reada=2. Both trees are being enumerated one after the other. > The prototype currently just uses raw bios, does not make use of the > page cache and does not enter the read pages into the cache. This will > probably add some overhead. It also does not check the crcs. > > While it is very promising to implement it for scrub, I think a more > general interface which can be used for every enumeration would be > beneficial. Use cases that come to mind are rebalance, reflink, deletion > of large files, listing of large directories etc.. > > I''d imagine an interface along the lines of > > int btrfs_readahead_init(struct btrfs_reada_ctx *reada); > int btrfs_readahead_add(struct btrfs_root *root, > struct btrfs_key *start, > struct btrfs_key *end, > struct btrfs_reada_ctx *reada); > void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); > > to trigger the readahead of parts of a tree. Multiple readahead > requests can be given before waiting. This would enable the very > beneficial folding seen above for ''reading both trees''. > > Also it would be possible to add a cascading readahead, where the > content of leaves would trigger readaheads in other trees, maybe by > giving a callback for the decisions what to read instead of the fixed > start/end range. > > For the implementation I''d need an interface which I haven''t been able > to find yet. Currently I can trigger the read of several pages / tree > blocks and wait for the completion of each of them. What I''d need would > be an interface that gives me a callback on each completion or a waiting > function that wakes up on each completion with the information which > pages just completed. > One way to achieve this would be to add a hook, but I gladly take any > implementation hints. > > -- > Arne > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen <sensille@gmx.net> wrote:> While looking into the performance of scrub I noticed that a significant > amount of time is being used for loading the extent tree and the csum > tree. While this is no surprise I did some prototyping on how to improve > on it. > The main idea is to load the tree (or parts of it) top-down, order the > needed blocks and distribute it over all disks. > To keep you interested, some results first. > > a) by tree enumeration with reada=2 > reading extent tree: 242s > reading csum tree: 140s > reading both trees: 324s > > b) prefetch prototype > reading extent tree: 23.5s > reading csum tree: 20.4s > reading both trees: 25.7s10x speed-up looks indeed impressive. Just for me to be sure, did I get you right in that you attribute this effect specifically to enumerating tree leaves in key address vs. disk addresses when these two are not aligned? Regards, Andrey> > The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled > 28%. It is created with the current git tree + the round robin patch and > filled with > > fs_mark -D 512 -t 16 -n 4096 -F -S0 > > The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() > with path->reada=2. Both trees are being enumerated one after the other. > The prototype currently just uses raw bios, does not make use of the > page cache and does not enter the read pages into the cache. This will > probably add some overhead. It also does not check the crcs. > > While it is very promising to implement it for scrub, I think a more > general interface which can be used for every enumeration would be > beneficial. Use cases that come to mind are rebalance, reflink, deletion > of large files, listing of large directories etc.. > > I''d imagine an interface along the lines of > > int btrfs_readahead_init(struct btrfs_reada_ctx *reada); > int btrfs_readahead_add(struct btrfs_root *root, > struct btrfs_key *start, > struct btrfs_key *end, > struct btrfs_reada_ctx *reada); > void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); > > to trigger the readahead of parts of a tree. Multiple readahead > requests can be given before waiting. This would enable the very > beneficial folding seen above for ''reading both trees''. > > Also it would be possible to add a cascading readahead, where the > content of leaves would trigger readaheads in other trees, maybe by > giving a callback for the decisions what to read instead of the fixed > start/end range. > > For the implementation I''d need an interface which I haven''t been able > to find yet. Currently I can trigger the read of several pages / tree > blocks and wait for the completion of each of them. What I''d need would > be an interface that gives me a callback on each completion or a waiting > function that wakes up on each completion with the information which > pages just completed. > One way to achieve this would be to add a hook, but I gladly take any > implementation hints. > > -- > Arne > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Excerpts from Arne Jansen''s message of 2011-03-23 09:06:02 -0400:> While looking into the performance of scrub I noticed that a significant > amount of time is being used for loading the extent tree and the csum > tree. While this is no surprise I did some prototyping on how to improve > on it. > The main idea is to load the tree (or parts of it) top-down, order the > needed blocks and distribute it over all disks. > To keep you interested, some results first. > > a) by tree enumeration with reada=2 > reading extent tree: 242s > reading csum tree: 140s > reading both trees: 324s > > b) prefetch prototype > reading extent tree: 23.5s > reading csum tree: 20.4s > reading both trees: 25.7sVery nice, btrfsck does something similar.> > The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled > 28%. It is created with the current git tree + the round robin patch and > filled with > > fs_mark -D 512 -t 16 -n 4096 -F -S0 > > The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() > with path->reada=2. Both trees are being enumerated one after the other. > The prototype currently just uses raw bios, does not make use of the > page cache and does not enter the read pages into the cache. This will > probably add some overhead. It also does not check the crcs. > > While it is very promising to implement it for scrub, I think a more > general interface which can be used for every enumeration would be > beneficial. Use cases that come to mind are rebalance, reflink, deletion > of large files, listing of large directories etc.. > > I''d imagine an interface along the lines of > > int btrfs_readahead_init(struct btrfs_reada_ctx *reada); > int btrfs_readahead_add(struct btrfs_root *root, > struct btrfs_key *start, > struct btrfs_key *end, > struct btrfs_reada_ctx *reada); > void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); > > to trigger the readahead of parts of a tree. Multiple readahead > requests can be given before waiting. This would enable the very > beneficial folding seen above for ''reading both trees''. > > Also it would be possible to add a cascading readahead, where the > content of leaves would trigger readaheads in other trees, maybe by > giving a callback for the decisions what to read instead of the fixed > start/end range. > > For the implementation I''d need an interface which I haven''t been able > to find yet. Currently I can trigger the read of several pages / tree > blocks and wait for the completion of each of them. What I''d need would > be an interface that gives me a callback on each completion or a waiting > function that wakes up on each completion with the information which > pages just completed. > One way to achieve this would be to add a hook, but I gladly take any > implementation hints.We have the bio endio call backs for this, I think that''s the only thing you can use. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 23.03.2011 20:26, Andrey Kuzmin wrote:> On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen<sensille@gmx.net> wrote: >> While looking into the performance of scrub I noticed that a significant >> amount of time is being used for loading the extent tree and the csum >> tree. While this is no surprise I did some prototyping on how to improve >> on it. >> The main idea is to load the tree (or parts of it) top-down, order the >> needed blocks and distribute it over all disks. >> To keep you interested, some results first. >> >> a) by tree enumeration with reada=2 >> reading extent tree: 242s >> reading csum tree: 140s >> reading both trees: 324s >> >> b) prefetch prototype >> reading extent tree: 23.5s >> reading csum tree: 20.4s >> reading both trees: 25.7s > > 10x speed-up looks indeed impressive. Just for me to be sure, did I > get you right in that you attribute this effect specifically to > enumerating tree leaves in key address vs. disk addresses when these > two are not aligned?Yes. Leaves and the intermediate nodes tend to be quite scattered around the disk with respect to their logical order. Reading them in logical (ascending/descending) order require lots of seeks.> > Regards, > Andrey > >> >> The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled >> 28%. It is created with the current git tree + the round robin patch and >> filled with >> >> fs_mark -D 512 -t 16 -n 4096 -F -S0 >> >> The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() >> with path->reada=2. Both trees are being enumerated one after the other. >> The prototype currently just uses raw bios, does not make use of the >> page cache and does not enter the read pages into the cache. This will >> probably add some overhead. It also does not check the crcs. >> >> While it is very promising to implement it for scrub, I think a more >> general interface which can be used for every enumeration would be >> beneficial. Use cases that come to mind are rebalance, reflink, deletion >> of large files, listing of large directories etc.. >> >> I''d imagine an interface along the lines of >> >> int btrfs_readahead_init(struct btrfs_reada_ctx *reada); >> int btrfs_readahead_add(struct btrfs_root *root, >> struct btrfs_key *start, >> struct btrfs_key *end, >> struct btrfs_reada_ctx *reada); >> void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); >> >> to trigger the readahead of parts of a tree. Multiple readahead >> requests can be given before waiting. This would enable the very >> beneficial folding seen above for ''reading both trees''. >> >> Also it would be possible to add a cascading readahead, where the >> content of leaves would trigger readaheads in other trees, maybe by >> giving a callback for the decisions what to read instead of the fixed >> start/end range. >> >> For the implementation I''d need an interface which I haven''t been able >> to find yet. Currently I can trigger the read of several pages / tree >> blocks and wait for the completion of each of them. What I''d need would >> be an interface that gives me a callback on each completion or a waiting >> function that wakes up on each completion with the information which >> pages just completed. >> One way to achieve this would be to add a hook, but I gladly take any >> implementation hints. >> >> -- >> Arne >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Mar 23, 2011 at 11:28 PM, Arne Jansen <sensille@gmx.net> wrote:> On 23.03.2011 20:26, Andrey Kuzmin wrote: >> >> On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen<sensille@gmx.net> wrote: >>> >>> While looking into the performance of scrub I noticed that a significant >>> amount of time is being used for loading the extent tree and the csum >>> tree. While this is no surprise I did some prototyping on how to improve >>> on it. >>> The main idea is to load the tree (or parts of it) top-down, order the >>> needed blocks and distribute it over all disks. >>> To keep you interested, some results first. >>> >>> a) by tree enumeration with reada=2 >>> reading extent tree: 242s >>> reading csum tree: 140s >>> reading both trees: 324s >>> >>> b) prefetch prototype >>> reading extent tree: 23.5s >>> reading csum tree: 20.4s >>> reading both trees: 25.7s >> >> 10x speed-up looks indeed impressive. Just for me to be sure, did I >> get you right in that you attribute this effect specifically to >> enumerating tree leaves in key address vs. disk addresses when these >> two are not aligned? > > Yes. Leaves and the intermediate nodes tend to be quite scattered > around the disk with respect to their logical order. > Reading them in logical (ascending/descending) order require lots > of seeks.And the patch actually does on-the-fly defragmentation, right? Why loose it then :)? Regards, Andrey> >> >> Regards, >> Andrey >> >>> >>> The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled >>> 28%. It is created with the current git tree + the round robin patch and >>> filled with >>> >>> fs_mark -D 512 -t 16 -n 4096 -F -S0 >>> >>> The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() >>> with path->reada=2. Both trees are being enumerated one after the other. >>> The prototype currently just uses raw bios, does not make use of the >>> page cache and does not enter the read pages into the cache. This will >>> probably add some overhead. It also does not check the crcs. >>> >>> While it is very promising to implement it for scrub, I think a more >>> general interface which can be used for every enumeration would be >>> beneficial. Use cases that come to mind are rebalance, reflink, deletion >>> of large files, listing of large directories etc.. >>> >>> I''d imagine an interface along the lines of >>> >>> int btrfs_readahead_init(struct btrfs_reada_ctx *reada); >>> int btrfs_readahead_add(struct btrfs_root *root, >>> struct btrfs_key *start, >>> struct btrfs_key *end, >>> struct btrfs_reada_ctx *reada); >>> void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); >>> >>> to trigger the readahead of parts of a tree. Multiple readahead >>> requests can be given before waiting. This would enable the very >>> beneficial folding seen above for ''reading both trees''. >>> >>> Also it would be possible to add a cascading readahead, where the >>> content of leaves would trigger readaheads in other trees, maybe by >>> giving a callback for the decisions what to read instead of the fixed >>> start/end range. >>> >>> For the implementation I''d need an interface which I haven''t been able >>> to find yet. Currently I can trigger the read of several pages / tree >>> blocks and wait for the completion of each of them. What I''d need would >>> be an interface that gives me a callback on each completion or a waiting >>> function that wakes up on each completion with the information which >>> pages just completed. >>> One way to achieve this would be to add a hook, but I gladly take any >>> implementation hints. >>> >>> -- >>> Arne >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On wed, 23 Mar 2011 21:28:25 +0100, Arne Jansen wrote:> On 23.03.2011 20:26, Andrey Kuzmin wrote: >> On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen<sensille@gmx.net> wrote: >>> While looking into the performance of scrub I noticed that a significant >>> amount of time is being used for loading the extent tree and the csum >>> tree. While this is no surprise I did some prototyping on how to improve >>> on it. >>> The main idea is to load the tree (or parts of it) top-down, order the >>> needed blocks and distribute it over all disks. >>> To keep you interested, some results first. >>> >>> a) by tree enumeration with reada=2 >>> reading extent tree: 242s >>> reading csum tree: 140s >>> reading both trees: 324s >>> >>> b) prefetch prototype >>> reading extent tree: 23.5s >>> reading csum tree: 20.4s >>> reading both trees: 25.7s >> >> 10x speed-up looks indeed impressive. Just for me to be sure, did I >> get you right in that you attribute this effect specifically to >> enumerating tree leaves in key address vs. disk addresses when these >> two are not aligned? > > Yes. Leaves and the intermediate nodes tend to be quite scattered > around the disk with respect to their logical order. > Reading them in logical (ascending/descending) order require lots > of seeks.I''m also dealing with tree fragmentation problem, I try to store the leaves which have the same parent closely. Regards Miao> >> >> Regards, >> Andrey >> >>> >>> The test setup consists of a 7 Seagate ES.2 1TB disks filesystem, filled >>> 28%. It is created with the current git tree + the round robin patch and >>> filled with >>> >>> fs_mark -D 512 -t 16 -n 4096 -F -S0 >>> >>> The ''normal'' read is done by enumerating the leaves by btrfs_next_leaf() >>> with path->reada=2. Both trees are being enumerated one after the other. >>> The prototype currently just uses raw bios, does not make use of the >>> page cache and does not enter the read pages into the cache. This will >>> probably add some overhead. It also does not check the crcs. >>> >>> While it is very promising to implement it for scrub, I think a more >>> general interface which can be used for every enumeration would be >>> beneficial. Use cases that come to mind are rebalance, reflink, deletion >>> of large files, listing of large directories etc.. >>> >>> I''d imagine an interface along the lines of >>> >>> int btrfs_readahead_init(struct btrfs_reada_ctx *reada); >>> int btrfs_readahead_add(struct btrfs_root *root, >>> struct btrfs_key *start, >>> struct btrfs_key *end, >>> struct btrfs_reada_ctx *reada); >>> void btrfs_readahead_wait(struct btrfs_reada_ctx *reada); >>> >>> to trigger the readahead of parts of a tree. Multiple readahead >>> requests can be given before waiting. This would enable the very >>> beneficial folding seen above for ''reading both trees''. >>> >>> Also it would be possible to add a cascading readahead, where the >>> content of leaves would trigger readaheads in other trees, maybe by >>> giving a callback for the decisions what to read instead of the fixed >>> start/end range. >>> >>> For the implementation I''d need an interface which I haven''t been able >>> to find yet. Currently I can trigger the read of several pages / tree >>> blocks and wait for the completion of each of them. What I''d need would >>> be an interface that gives me a callback on each completion or a waiting >>> function that wakes up on each completion with the information which >>> pages just completed. >>> One way to achieve this would be to add a hook, but I gladly take any >>> implementation hints. >>> >>> -- >>> Arne >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 24.03.2011 02:38, Miao Xie wrote:> On wed, 23 Mar 2011 21:28:25 +0100, Arne Jansen wrote: >> On 23.03.2011 20:26, Andrey Kuzmin wrote: >>> On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen<sensille@gmx.net> wrote: >>>> The main idea is to load the tree (or parts of it) top-down, order the >>>> needed blocks and distribute it over all disks. >>>> To keep you interested, some results first. >>>> >>>> a) by tree enumeration with reada=2 >>>> reading extent tree: 242s >>>> reading csum tree: 140s >>>> reading both trees: 324s >>>> >>>> b) prefetch prototype >>>> reading extent tree: 23.5s >>>> reading csum tree: 20.4s >>>> reading both trees: 25.7s >>> >>> 10x speed-up looks indeed impressive. Just for me to be sure, did I >>> get you right in that you attribute this effect specifically to >>> enumerating tree leaves in key address vs. disk addresses when these >>> two are not aligned? >> >> Yes. Leaves and the intermediate nodes tend to be quite scattered >> around the disk with respect to their logical order. >> Reading them in logical (ascending/descending) order require lots >> of seeks. > > I''m also dealing with tree fragmentation problem, I try to store the leaves > which have the same parent closely.That''s good to hear. Do you have already anything I can repeat the test with? -Arne> > Regards > Miao >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On thu, 24 Mar 2011 08:29:57 +0100, Arne Jansen wrote:> On 24.03.2011 02:38, Miao Xie wrote: >> On wed, 23 Mar 2011 21:28:25 +0100, Arne Jansen wrote: >>> On 23.03.2011 20:26, Andrey Kuzmin wrote: >>>> On Wed, Mar 23, 2011 at 4:06 PM, Arne Jansen<sensille@gmx.net> wrote: >>>>> The main idea is to load the tree (or parts of it) top-down, order the >>>>> needed blocks and distribute it over all disks. >>>>> To keep you interested, some results first. >>>>> >>>>> a) by tree enumeration with reada=2 >>>>> reading extent tree: 242s >>>>> reading csum tree: 140s >>>>> reading both trees: 324s >>>>> >>>>> b) prefetch prototype >>>>> reading extent tree: 23.5s >>>>> reading csum tree: 20.4s >>>>> reading both trees: 25.7s >>>> >>>> 10x speed-up looks indeed impressive. Just for me to be sure, did I >>>> get you right in that you attribute this effect specifically to >>>> enumerating tree leaves in key address vs. disk addresses when these >>>> two are not aligned? >>> >>> Yes. Leaves and the intermediate nodes tend to be quite scattered >>> around the disk with respect to their logical order. >>> Reading them in logical (ascending/descending) order require lots >>> of seeks. >> >> I''m also dealing with tree fragmentation problem, I try to store the leaves >> which have the same parent closely. > > That''s good to hear. Do you have already anything I can repeat the test > with?It is still under developing.;) Thanks Miao> -Arne > >> >> Regards >> Miao >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 23.03.2011 20:32, Chris Mason wrote:> Excerpts from Arne Jansen''s message of 2011-03-23 09:06:02 -0400: >> >> For the implementation I''d need an interface which I haven''t been able >> to find yet. Currently I can trigger the read of several pages / tree >> blocks and wait for the completion of each of them. What I''d need would >> be an interface that gives me a callback on each completion or a waiting >> function that wakes up on each completion with the information which >> pages just completed. >> One way to achieve this would be to add a hook, but I gladly take any >> implementation hints. > > We have the bio endio call backs for this, I think that''s the only thing > you can use. >ok, so I''ll add a new extent state bit EXTENT_READAHEAD and test for it in btree_readpage_end_io_hook. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Excerpts from Arne Jansen''s message of 2011-03-25 16:14:35 -0400:> On 23.03.2011 20:32, Chris Mason wrote: > > Excerpts from Arne Jansen''s message of 2011-03-23 09:06:02 -0400: > >> > >> For the implementation I''d need an interface which I haven''t been able > >> to find yet. Currently I can trigger the read of several pages / tree > >> blocks and wait for the completion of each of them. What I''d need would > >> be an interface that gives me a callback on each completion or a waiting > >> function that wakes up on each completion with the information which > >> pages just completed. > >> One way to achieve this would be to add a hook, but I gladly take any > >> implementation hints. > > > > We have the bio endio call backs for this, I think that''s the only thing > > you can use. > > > > ok, so I''ll add a new extent state bit EXTENT_READAHEAD and test for it > in btree_readpage_end_io_hook.It''s also common to use a chain of endio handlers. If you''re allocating any state for the RA, you just save the original endio handler in your new struct, and then use your own endio handler that does the readahead smarts. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 25.03.2011 21:15, Chris Mason wrote:> Excerpts from Arne Jansen''s message of 2011-03-25 16:14:35 -0400: >> On 23.03.2011 20:32, Chris Mason wrote: >>> Excerpts from Arne Jansen''s message of 2011-03-23 09:06:02 -0400: >>>> >>>> For the implementation I''d need an interface which I haven''t been able >>>> to find yet. Currently I can trigger the read of several pages / tree >>>> blocks and wait for the completion of each of them. What I''d need would >>>> be an interface that gives me a callback on each completion or a waiting >>>> function that wakes up on each completion with the information which >>>> pages just completed. >>>> One way to achieve this would be to add a hook, but I gladly take any >>>> implementation hints. >>> >>> We have the bio endio call backs for this, I think that''s the only thing >>> you can use. >>> >> >> ok, so I''ll add a new extent state bit EXTENT_READAHEAD and test for it >> in btree_readpage_end_io_hook. > > It''s also common to use a chain of endio handlers. If you''re allocating > any state for the RA, you just save the original endio handler in your > new struct, and then use your own endio handler that does the readahead > smarts. >Do you mean replacing the bio end_io handler or the readpage_end_io_hook? As I want the pages to end up in the page cache, I''d like to use as much of the existing infrastructure as possible. To intercept the bio deep down in the chain would mean to duplicate some code on the way down and on the way up again. -Arne -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Excerpts from Arne Jansen''s message of 2011-03-25 16:53:24 -0400:> On 25.03.2011 21:15, Chris Mason wrote: > > Excerpts from Arne Jansen''s message of 2011-03-25 16:14:35 -0400: > >> On 23.03.2011 20:32, Chris Mason wrote: > >>> Excerpts from Arne Jansen''s message of 2011-03-23 09:06:02 -0400: > >>>> > >>>> For the implementation I''d need an interface which I haven''t been able > >>>> to find yet. Currently I can trigger the read of several pages / tree > >>>> blocks and wait for the completion of each of them. What I''d need would > >>>> be an interface that gives me a callback on each completion or a waiting > >>>> function that wakes up on each completion with the information which > >>>> pages just completed. > >>>> One way to achieve this would be to add a hook, but I gladly take any > >>>> implementation hints. > >>> > >>> We have the bio endio call backs for this, I think that''s the only thing > >>> you can use. > >>> > >> > >> ok, so I''ll add a new extent state bit EXTENT_READAHEAD and test for it > >> in btree_readpage_end_io_hook. > > > > It''s also common to use a chain of endio handlers. If you''re allocating > > any state for the RA, you just save the original endio handler in your > > new struct, and then use your own endio handler that does the readahead > > smarts. > > > > Do you mean replacing the bio end_io handler or the > readpage_end_io_hook? As I want the pages to end up in the page cache, > I''d like to use as much of the existing infrastructure as possible. > To intercept the bio deep down in the chain would mean to duplicate > some code on the way down and on the way up again.The end_io handler, see how we chain them around for the crc helper threads. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html