[lkml]   [2017]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] Add slowpath enter/exit trace events
On 2017/11/23 22:36, Mel Gorman wrote:
> On Thu, Nov 23, 2017 at 01:25:30PM +0100, Michal Hocko wrote:
>> On Thu 23-11-17 11:43:36, wrote:
>>> From: Peter Enderborg <>
>>> The warning of slow allocation has been removed, this is
>>> a other way to fetch that information. But you need
>>> to enable the trace. The exit function also returns
>>> information about the number of retries, how long
>>> it was stalled and failure reason if that happened.
>> I think this is just too excessive. We already have a tracepoint for the
>> allocation exit. All we need is an entry to have a base to compare with.
>> Another usecase would be to measure allocation latency. Information you
>> are adding can be (partially) covered by existing tracepoints.
> You can gather that by simply adding a probe to __alloc_pages_slowpath
> (like what perf probe does) and matching the trigger with the existing
> mm_page_alloc points. This is a bit approximate because you would need
> to filter mm_page_alloc hits that do not have a corresponding hit with
> __alloc_pages_slowpath but that is easy.
> With that probe, it's trivial to use systemtap to track the latencies between
> those points on a per-processes basis and then only do a dump_stack from
> systemtap for the ones that are above a particular threshold. This can all
> be done without introducing state-tracking code into the page allocator
> that is active regardless of whether the tracepoint is in use. It also
> has the benefit of working with many older kernels.

Please see my attempt at .
Printing just current thread is not sufficient for me.

 \ /
  Last update: 2017-11-23 14:44    [W:0.107 / U:9.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site