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Message-ID: <87d2eecfdz.fsf@vitty.brq.redhat.com> Date: Thu, 12 Jun 2014 17:32:40 +0200 From: Vitaly Kuznetsov <vkuznets@...hat.com> To: Felipe Franciosi <felipe.franciosi@...rix.com> Cc: Roger Pau Monne <roger.pau@...rix.com>, "xen-devel\@lists.xenproject.org" <xen-devel@...ts.xenproject.org>, "axboe\@kernel.dk" <axboe@...nel.dk>, Greg KH <gregkh@...uxfoundation.org>, "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>, "stable\@vger.kernel.org" <stable@...r.kernel.org>, "jerry.snitselaar\@oracle.com" <jerry.snitselaar@...cle.com>, Jiri Slaby <jslaby@...e.cz>, Ronen Hod <rhod@...hat.com>, Andrew Jones <drjones@...hat.com> Subject: Re: [Xen-devel] Backport request to stable of two performance related fixes for xen-blkfront (3.13 fixes to earlier trees) Felipe Franciosi <felipe.franciosi@...rix.com> writes: > Hi Vitaly, > > Are you able to test a 3.10 guest with and without the backport that > Roger sent? This patch is attached to an e-mail Roger sent on "22 May > 2014 13:54". Sure, Now I'm comparing d642daf637d02dacf216d7fd9da7532a4681cfd3 and 46c0326164c98e556c35c3eb240273595d43425d commits from git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git (with and without two commits in question). The test is exactly the same as described before. The result is here: http://hadoop.ru/pubfiles/bug1096909/fusion/310_nopgrants_stripe.png as you can see 46c03261 (without patches) wins everywhere. > > Because your results are contradicting with what these patches are > meant to do, I would like to make sure that this isn't related to > something else that happened after 3.10. I still think Dom0 kernel and blktap/blktap3 is what make a difference between our test environments. > > You could also test Ubuntu Sancy guests with and without the patched kernels provided by Joseph Salisbury on launchpad: https://bugs.launchpad.net/bugs/1319003 > > Thanks, > Felipe > >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com] >> Sent: 12 June 2014 13:01 >> To: Roger Pau Monne >> Cc: xen-devel@...ts.xenproject.org; axboe@...nel.dk; Felipe Franciosi; Greg >> KH; linux-kernel@...r.kernel.org; stable@...r.kernel.org; >> jerry.snitselaar@...cle.com; Jiri Slaby; Ronen Hod; Andrew Jones >> Subject: Re: [Xen-devel] Backport request to stable of two performance >> related fixes for xen-blkfront (3.13 fixes to earlier trees) >> >> Roger Pau Monné <roger.pau@...rix.com> writes: >> >> > On 10/06/14 15:19, Vitaly Kuznetsov wrote: >> >> Vitaly Kuznetsov <vkuznets@...hat.com> writes: >> >> >> >>> Jiri Slaby <jslaby@...e.cz> writes: >> >>> >> >>>> On 06/04/2014 07:48 AM, Greg KH wrote: >> >>>>> On Wed, May 14, 2014 at 03:11:22PM -0400, Konrad Rzeszutek Wilk >> wrote: >> >>>>>> Hey Greg >> >>>>>> >> >>>>>> This email is in regards to backporting two patches to stable >> >>>>>> that fall under the 'performance' rule: >> >>>>>> >> >>>>>> bfe11d6de1c416cea4f3f0f35f864162063ce3fa >> >>>>>> fbe363c476afe8ec992d3baf682670a4bd1b6ce6 >> >>>>> >> >>>>> Now queued up, thanks. >> >>>> >> >>>> AFAIU, they introduce a performance regression. >> >>>> >> >>>> Vitaly? >> >>> >> >>> I'm aware of a performance regression in a 'very special' case when >> >>> ramdisks or files on tmpfs are being used as storage, I post my >> >>> results a while ago: >> >>> https://lkml.org/lkml/2014/5/22/164 >> >>> I'm not sure if that 'special' case requires investigation and/or >> >>> should prevent us from doing stable backport but it would be nice if >> >>> someone tries to reproduce it at least. >> >>> >> >>> I'm going to make a bunch of tests with FusionIO drives and >> >>> sequential read to replicate same test Felipe did, I'll report as >> >>> soon as I have data (beginning of next week hopefuly). >> >> >> >> Turns out the regression I'm observing with these patches is not >> >> restricted to tmpfs/ramdisk usage. >> >> >> >> I was doing tests with Fusion-io ioDrive Duo 320GB (Dual Adapter) on >> >> HP ProLiant DL380 G6 (2xE5540, 8G RAM). Hyperthreading is disabled, >> >> Dom0 is pinned to CPU0 (cores 0,1,2,3) I run up to 8 guests with 1 >> >> vCPU each, they are pinned to CPU1 (cores 4,5,6,7,4,5,6,7). I tried >> >> differed pinning (Dom0 to 0,1,4,5, DomUs to 2,3,6,7,2,3,6,7 to >> >> balance NUMA, that doesn't make any difference to the results). I was >> >> testing on top of Xen-4.3.2. >> >> >> >> I was testing two storage configurations: >> >> 1) Plain 10G partitions from one Fusion drive (/dev/fioa) are >> >> attached to guests >> >> 2) LVM group is created on top of both drives (/dev/fioa, /dev/fiob), >> >> 10G logical volumes are created with striping (lvcreate -i2 ...) >> >> >> >> Test is done by simultaneous fio run in guests (rw=read, direct=1) >> >> for >> >> 10 second. Each test was performed 3 times and the average was taken. >> >> Kernels I compare are: >> >> 1) v3.15-rc5-157-g60b5f90 unmodified >> >> 2) v3.15-rc5-157-g60b5f90 with >> 427bfe07e6744c058ce6fc4aa187cda96b635539, >> >> bfe11d6de1c416cea4f3f0f35f864162063ce3fa, and >> >> fbe363c476afe8ec992d3baf682670a4bd1b6ce6 reverted. >> >> >> >> First test was done with Dom0 with persistent grant support (Fedora's >> >> 3.14.4-200.fc20.x86_64): >> >> 1) Partitions: >> >> http://hadoop.ru/pubfiles/bug1096909/fusion/315_pgrants_partitions.pn >> >> g (same markers mean same bs, we get 860 MB/s here, patches make no >> >> difference, result matches expectation) >> >> >> >> 2) LVM Stripe: >> >> http://hadoop.ru/pubfiles/bug1096909/fusion/315_pgrants_stripe.png >> >> (1715 MB/s, patches make no difference, result matches expectation) >> >> >> >> Second test was performed with Dom0 without persistent grants support >> >> (Fedora's 3.7.9-205.fc18.x86_64) >> >> 1) Partitions: >> >> http://hadoop.ru/pubfiles/bug1096909/fusion/315_nopgrants_partitions. >> >> png >> >> (860 MB/sec again, patches worsen a bit overall throughput with 1-3 >> >> clients) >> >> >> >> 2) LVM Stripe: >> >> http://hadoop.ru/pubfiles/bug1096909/fusion/315_nopgrants_stripe.png >> >> (Here we see the same regression I observed with ramdisks and tmpfs >> >> files, unmodified kernel: 1550MB/s, with patches reverted: 1715MB/s). >> >> >> >> The only major difference with Felipe's test is that he was using >> >> blktap3 with XenServer and I'm using standard blktap2. >> > >> > Hello, >> > >> > I don't think you are using blktap2, I guess you are using blkback. >> >> Right, sorry for the confusion. >> >> > Also, running the test only for 10s and 3 repetitions seems too low, I >> > would probably try to run the tests for a longer time and do more >> > repetitions, and include the standard deviation also. >> > >> > Could you try to revert the patches independently to see if it's a >> > specific commit that introduces the regression? >> >> I did additional test runs. Now I'm comparing 3 kernels: >> 1) Unmodified v3.15-rc5-157-g60b5f90 - green color on chart >> >> 2) v3.15-rc5-157-g60b5f90 with bfe11d6de1c416cea4f3f0f35f864162063ce3fa >> and 427bfe07e6744c058ce6fc4aa187cda96b635539 reverted (so only >> fbe363c476afe8ec992d3baf682670a4bd1b6ce6 "xen-blkfront: revoke foreign >> access for grants not mapped by the backend" left) - blue color on chart >> >> 3) v3.15-rc5-157-g60b5f90 with all >> (bfe11d6de1c416cea4f3f0f35f864162063ce3fa, >> 427bfe07e6744c058ce6fc4aa187cda96b635539, >> fbe363c476afe8ec992d3baf682670a4bd1b6ce6) patches reverted - red color >> on chart. >> >> I test on top of striped LVM on 2 FusionIO drives, I do 3 repetitions for >> 30 seconds each. >> >> The result is here: >> http://hadoop.ru/pubfiles/bug1096909/fusion/315_nopgrants_20140612.pn >> g >> >> It is consistent with what I've measured with ramdrives and tmpfs files: >> >> 1) fbe363c476afe8ec992d3baf682670a4bd1b6ce6 "xen-blkfront: revoke >> foreign access for grants not mapped by the backend" brings us the >> regression. Bigger block size is - bigger the difference but the regression is >> observed with all block sizes > 8k. >> >> 2) bfe11d6de1c416cea4f3f0f35f864162063ce3fa "xen-blkfront: restore the >> non-persistent data path" brings us performance improvement but with >> conjunction with fbe363c476afe8ec992d3baf682670a4bd1b6ce6 it is still >> worse than the kernel without both patches. >> >> My Dom0 is Fedora's 3.7.9-205.fc18.x86_64. I can test on newer blkback, >> however I'm not aware of any way to disable persistent grants there (there is >> no regression when they're used). >> >> > >> > Thanks, Roger. >> >> Thanks, >> >> -- >> Vitaly -- Vitaly -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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