On 10/06/14 15:19, Vitaly Kuznetsov wrote: > Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes: > >> Jiri Slaby <jslaby@xxxxxxx> 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.png > (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. 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? Thanks, Roger. -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
