> On Aug 27, 2021, at 6:00 PM, Mike Javorski <mike.javorski@xxxxxxxxx> wrote:
>
> OK, an update. Several hours of spaced out testing sessions and the
> first patch seems to have resolved the issue. There may be a very tiny
> bit of lag that still occurs when opening/processing new files, but so
> far on this kernel I have not had any multi-second freezes. I am still
> waiting on the kernel with Neil's patch to compile (compiling on this
> underpowered server so it's taking several hours), but I think the
> testing there will just be to see if I can show it works still, and
> then to try and test in a memory constrained VM. To see if I can
> recreate Neil's experiment. Likely will have to do this over the
> weekend given the kernel compile delay + fiddling with a VM.
Thanks for your testing!
> Chuck: I don't mean to overstep bounds, but is it possible to get that
> patch pulled into 5.13 stable? That may help things for several people
> while 5.14 goes through it's shakedown in archlinux prior to release.
The patch had a Fixes: tag, so it should get automatically backported
to every kernel that has the broken commit. If you don't see it in
a subsequent 5.13 stable kernel, you are free to ask the stable
maintainers to consider it.
> - mike
>
> On Fri, Aug 27, 2021 at 10:07 AM Mike Javorski <mike.javorski@xxxxxxxxx> wrote:
>>
>> Chuck:
>> I just booted a 5.13.13 kernel with your suggested patch. No freezes
>> on the first test, but that sometimes happens so I will let the server
>> settle some and try it again later in the day (which also would align
>> with Neil's comment on memory fragmentation being a contributor).
>>
>> Neil:
>> I have started a compile with the above kernel + your patch to test
>> next unless you or Chuck determine that it isn't needed, or that I
>> should test both patches discreetly. As the above is already merged to
>> 5.14 it seemed logical to just add your patch on top.
>>
>> I will also try to set up a vm to test your md5sum scenario with the
>> various kernels since it's a much faster thing to test.
>>
>> - mike
>>
>> On Fri, Aug 27, 2021 at 7:13 AM Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>>>
>>>
>>>> On Aug 27, 2021, at 3:14 AM, NeilBrown <neilb@xxxxxxx> wrote:
>>>>
>>>> Subject: [PATCH] SUNRPC: don't pause on incomplete allocation
>>>>
>>>> alloc_pages_bulk_array() attempts to allocate at least one page based on
>>>> the provided pages, and then opportunistically allocates more if that
>>>> can be done without dropping the spinlock.
>>>>
>>>> So if it returns fewer than requested, that could just mean that it
>>>> needed to drop the lock. In that case, try again immediately.
>>>>
>>>> Only pause for a time if no progress could be made.
>>>
>>> The case I was worried about was "no pages available on the
>>> pcplist", in which case, alloc_pages_bulk_array() resorts
>>> to calling __alloc_pages() and returns only one new page.
>>>
>>> "No progess" would mean even __alloc_pages() failed.
>>>
>>> So this patch would behave essentially like the
>>> pre-alloc_pages_bulk_array() code: call alloc_page() for
>>> each empty struct_page in the array without pausing. That
>>> seems correct to me.
>>>
>>>
>>> I would add
>>>
>>> Fixes: f6e70aab9dfe ("SUNRPC: refresh rq_pages using a bulk page allocator")
>>>
>>>
>>>> Signed-off-by: NeilBrown <neilb@xxxxxxx>
>>>> ---
>>>> net/sunrpc/svc_xprt.c | 7 +++++--
>>>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
>>>> index d66a8e44a1ae..99268dd95519 100644
>>>> --- a/net/sunrpc/svc_xprt.c
>>>> +++ b/net/sunrpc/svc_xprt.c
>>>> @@ -662,7 +662,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
>>>> {
>>>> struct svc_serv *serv = rqstp->rq_server;
>>>> struct xdr_buf *arg = &rqstp->rq_arg;
>>>> - unsigned long pages, filled;
>>>> + unsigned long pages, filled, prev;
>>>>
>>>> pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
>>>> if (pages > RPCSVC_MAXPAGES) {
>>>> @@ -672,11 +672,14 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
>>>> pages = RPCSVC_MAXPAGES;
>>>> }
>>>>
>>>> - for (;;) {
>>>> + for (prev = 0;; prev = filled) {
>>>> filled = alloc_pages_bulk_array(GFP_KERNEL, pages,
>>>> rqstp->rq_pages);
>>>> if (filled == pages)
>>>> break;
>>>> + if (filled > prev)
>>>> + /* Made progress, don't sleep yet */
>>>> + continue;
>>>>
>>>> set_current_state(TASK_INTERRUPTIBLE);
>>>> if (signalled() || kthread_should_stop()) {
>>>
>>> --
>>> Chuck Lever
>>>
>>>
>>>
--
Chuck Lever
