similar to: How commonly applications make use of fadvise?

On Fri, Aug 11, 2017 at 12:47:47AM -0400, Raghavendra Gowdappa wrote: > 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

On 08/11/2017 04:51 PM, Niels de Vos wrote: > On Fri, Aug 11, 2017 at 12:47:47AM -0400, Raghavendra Gowdappa wrote: >> 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

On Fri, Aug 11, 2017 at 05:50:47PM +0530, Ravishankar N wrote: > > > On 08/11/2017 04:51 PM, Niels de Vos wrote: > > On Fri, Aug 11, 2017 at 12:47:47AM -0400, Raghavendra Gowdappa wrote: > > > Hi all, > > > > > > In a conversation between me, Milind and Csaba, Milind pointed out > > > fadvise(2) [1] and its potential benefits to Glusterfs'

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,

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

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

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

On Sat, Aug 19, 2017 at 4:27 PM, Csaba Henk <chenk at redhat.com> wrote: > Hi Niels, > > On Fri, Aug 11, 2017 at 2:33 PM, Niels de Vos <ndevos at redhat.com> wrote: > > On Fri, Aug 11, 2017 at 05:50:47PM +0530, Ravishankar N wrote: > [...] > >> To me it looks like fadvise (mm/fadvise.c) affects only the linux page > cache > >> behavior and is

Hi Niels, On Fri, Aug 11, 2017 at 2:33 PM, Niels de Vos <ndevos at redhat.com> wrote: > On Fri, Aug 11, 2017 at 05:50:47PM +0530, Ravishankar N wrote: [...] >> To me it looks like fadvise (mm/fadvise.c) affects only the linux page cache >> behavior and is decoupled from the filesystem itself. What this means for >> fuse is that the 'advise' is only to the

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 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 Milind, My suggestion just for your concern that if you eliminate the default block, a block associated with a case value will become the default block of the swhich instruction, since a switch instruction always requires a default block. But when a block associated with a case value become the default block, the associated case value is lost and may confuse the later optimizations such as

Hongbin Can you elaborate more on your suggestion? I am not sure I fully understand what you suggested. -Milind On Wed, Jul 17, 2013 at 11:11 PM, Hongbin Zheng <etherzhhb at gmail.com> wrote: > Hi Milind, > > Maybe you could annotate the default case value as metadata to the swith > instruction. > > Thanks > Hongbin > > > On Thu, Jul 18, 2013 at 1:09 PM,

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

Hi Milind, Maybe you could annotate the default case value as metadata to the swith instruction. Thanks Hongbin On Thu, Jul 18, 2013 at 1:09 PM, Milind Chabbi <Milind.Chabbi at rice.edu>wrote: > Hi Mark, > > This will workaround the problem of "default" branch restriction on > the switch instruction. The trouble with this technique is that it > will trump later

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

Hi Mark, This will workaround the problem of "default" branch restriction on the switch instruction. The trouble with this technique is that it will trump later optimization phases such as constant propagation. When a block was part of a case, because of the knowledge of the case value, the block was a candidate for better optimization. However, when we move the body of the case into

On Jul 17, 2013, at 9:01 PM, Milind Chabbi <Milind.Chabbi at rice.edu> wrote: > I am performing a transformation that requires changing the targets of > a basic block ending with a switch instruction. > In particular, I need to delete the edge that goes to the "default" > basic block. > But, LLVM switch instruction always wants a default target basic block > for a