similar to: DO NOT REPLY [Bug 7004] New: Use posix_fadvise to free cached file contents when done

While going through an old todo list I found that these patches had fallen by the way-side. About a year ago I initiated a discussion[1] with the Linux kernel folks regarding the lack of any useable fadvise support on the kernel side. As a result, I was observing extremely poor performance on my server after backup as executable pages were being swapped out in favor of data waiting to be flushed

You can use these flags as described in the manual page to optimize access patterns, and to get better behaviour with the page cache in some scenarios. For my testing I used the cachedel and cachestats utilities written by Julius Plenz (https://github.com/Feh/nocache). I started with a 32 GB file of random data on a machine with about 32 GB of RAM. At the beginning of the test I evicted the

On Fri, Aug 07, 2020 at 07:53:13AM -0500, Eric Blake wrote: > >$ free -m; time ./nbdkit file /var/tmp/random fadvise=sequential cache=none --run 'qemu-img convert -n -p -m 16 -W $nbd "json:{\"file.driver\":\"null-co\",\"file.size\":\"1E\"}"' ; free -m ; cachestats /var/tmp/random > > Hmm - the -W actually says that qemu-img is

Warning for kernel folks: I'm not much of an mm person; let me know if I got anything horribly wrong. Many folks use rsync in their nightly backup jobs. In these applications, speed is of minimal concern and should be sacrificed in order to minimize the effect of rsync on the rest of the machine. When rsync is working on a large directory it can quickly fill the page cache with written data,

The new cache=none mode is misleading since it does not avoid usage of the page cache. When using shared storage, we may get stale data from the page cache. When writing, we flush after every write which is inefficient and unneeded. Rename the cache modes to: - writeback - write complete when the system call returned, and the data was copied to the page cache. - writethrough - write completes

Add wrappers around posix_fadvise and use them in places we were calling posix_fadvise directly before. Also in virt-builder we were doing this (and ignoring the result): posix_fadvise (fd, 0, 0, POSIX_FADV_RANDOM|POSIX_FADV_DONTNEED); However the POSIX_FADV_* flags are _not_ bitmasks! In fact POSIX_FADV_RANDOM|POSIX_FADV_DONTNEED == POSIX_FADV_NOREUSE so we were giving a completely

The way we used posix_fadvise was wrong, and yet right! Rich.

I've recently been trying to track down the root cause of my server's persistent issue of thrashing horribly after being left inactive. It seems that the issue is likely my nightly backup schedule (using rsync) which traverses my entire 50GB home directory. I was surprised to find that rsync does not use fadvise to notify the kernel of its use-once data usage pattern. It looks like a

https://bugzilla.samba.org/show_bug.cgi?id=7876 Summary: please implement o_direct Product: rsync Version: 3.1.0 Platform: Other OS/Version: Linux Status: NEW Severity: normal Priority: P3 Component: core AssignedTo: wayned at samba.org ReportedBy: costinel at gmail.com QAContact:

On Fri, Aug 7, 2020, 16:16 Richard W.M. Jones <rjones@redhat.com> wrote: > On Fri, Aug 07, 2020 at 07:53:13AM -0500, Eric Blake wrote: > > >$ free -m; time ./nbdkit file /var/tmp/random fadvise=sequential > cache=none --run 'qemu-img convert -n -p -m 16 -W $nbd >

On 8/7/20 6:31 AM, Richard W.M. Jones wrote: > You can use these flags as described in the manual page to optimize > access patterns, and to get better behaviour with the page cache in > some scenarios. And if you guess wrong, it is only a performance penalty, not a correctness issue. > > For my testing I used the cachedel and cachestats utilities written by > Julius Plenz

Hi List, I have updated my rsync fadvise patch which stops rsync from ousting all your other data from cache when running large jobs. I have also written an article about the whole issue. http://insights.oetiker.ch/linux/fadvise.html cheers tobi -- Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten http://it.oetiker.ch tobi@oetiker.ch ++41 62 213 9902

Hi List, I am using rsync for hard-link backup. I found that there is a major problem with frequent backup filling up the file system cache with all the data from the files being backed up. The effect is that all the other 'sensible' data in the cache gets thrown out in the process. This is rather unfortunate as the performance of the system becomes very bad after running rsync. Some

On Sat, Aug 08, 2020 at 01:24:02AM +0300, Nir Soffer wrote: > The new cache=none mode is misleading since it does not avoid usage of > the page cache. When using shared storage, we may get stale data from > the page cache. When writing, we flush after every write which is > inefficient and unneeded. > Hmm. This isn't actually what the cache=none parameter is currently doing.

Hi all, In a conversation between me, Milind and Csaba, Milind pointed out fadvise(2) [1] and its potential benefits to Glusterfs' caching translators like read-ahead etc. After discussing about it, we agreed that our performance translators can leverage the hints to provide better performance. Now the question is how commonly applications actually provide hints? Is it something that is used

On Wed, Oct 23, 2013 at 03:38:30AM +0100, Pádraig Brady wrote: [...] By the way, Eric Sandeen solved the problem. It's a genuine misfeature in ext4 called auto_da_alloc which causes a flush on close if the file has been truncated (ftruncate or O_TRUNC) and the file size is zero bytes. I added these patches which work around the issue:

--- pxzcat.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/pxzcat.c b/pxzcat.c index 4ab8689..9bcdc36 100644 --- a/pxzcat.c +++ b/pxzcat.c @@ -29,10 +29,11 @@ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ +#define _GNU_SOURCE #include <config.h>

On Fri, Aug 07, 2020 at 04:43:12PM +0300, Nir Soffer wrote: > On Fri, Aug 7, 2020, 16:16 Richard W.M. Jones <rjones@redhat.com> wrote: > > I'm not sure if or even how we could ever do a robust O_DIRECT > > > > We can let the plugin an filter deal with that. The simplest solution is to > drop it on the user and require aligned requests. I mean this is very error

--- pxzcat.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/pxzcat.c b/pxzcat.c index 9bcdc36..55ccfc0 100644 --- a/pxzcat.c +++ b/pxzcat.c @@ -44,10 +44,11 @@ #include <sys/types.h> #include <error.h> #include <errno.h> #include <getopt.h> #include <pthread.h> +#include <linux/falloc.h> #include <lzma.h> #define DEBUG

On Sun, Aug 9, 2020 at 12:28 AM Richard W.M. Jones <rjones@redhat.com> wrote: > > On Sat, Aug 08, 2020 at 01:24:02AM +0300, Nir Soffer wrote: > > The new cache=none mode is misleading since it does not avoid usage of > > the page cache. When using shared storage, we may get stale data from > > the page cache. When writing, we flush after every write which is > >