On 04.06.25 14:00, Johannes Weiner wrote:
On Fri, May 30, 2025 at 07:52:28PM +1200, Barry Song wrote:
On Fri, May 30, 2025 at 9:14 AM Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
On Thu, May 29, 2025 at 04:28:46PM +0100, Matthew Wilcox wrote:
Barry's problem is that we're all nervous about possibly regressing
performance on some unknown workloads. Just try Barry's proposal, see
if anyone actually compains or if we're just afraid of our own shadows.
I actually explained why I think this is a terrible idea. But okay, I
tried the patch anyway.
This is 'git log' on a hot kernel repo after a large IO stream:
VANILLA BARRY
Real time 49.93 ( +0.00%) 60.36 ( +20.48%)
User time 32.10 ( +0.00%) 32.09 ( -0.04%)
System time 14.41 ( +0.00%) 14.64 ( +1.50%)
pgmajfault 9227.00 ( +0.00%) 18390.00 ( +99.30%)
workingset_refault_file 184.00 ( +0.00%) 236899.00 (+127954.05%)
Clearly we can't generally ignore page cache hits just because the
mmaps() are intermittent.
Hi Johannes,
Thanks!
Are you on v1, which lacks folio demotion[1], or v2, which includes it [2]?
[1] https://lore.kernel.org/linux-mm/20250412085852.48524-1-21cnbao@xxxxxxxxx/
[2] https://lore.kernel.org/linux-mm/20250514070820.51793-1-21cnbao@xxxxxxxxx/
The subthread is about whether the reference dismissal / demotion
should be unconditional (v1) or opt-in (v2).
I'm arguing for v2.
+1
--
Cheers,
David / dhildenb
