[lkml]   [2019]   [Jul]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH REBASED] mm, memcg: Make scan aggression always exclude protection
On Fri, Mar 22, 2019 at 04:03:07PM +0000, Chris Down wrote:
> This patch is an incremental improvement on the existing
> memory.{low,min} relative reclaim work to base its scan pressure
> calculations on how much protection is available compared to the current
> usage, rather than how much the current usage is over some protection
> threshold.
> Previously the way that memory.low protection works is that if you are
> 50% over a certain baseline, you get 50% of your normal scan pressure.
> This is certainly better than the previous cliff-edge behaviour, but it
> can be improved even further by always considering memory under the
> currently enforced protection threshold to be out of bounds. This means
> that we can set relatively low memory.low thresholds for variable or
> bursty workloads while still getting a reasonable level of protection,
> whereas with the previous version we may still trivially hit the 100%
> clamp. The previous 100% clamp is also somewhat arbitrary, whereas this
> one is more concretely based on the currently enforced protection
> threshold, which is likely easier to reason about.
> There is also a subtle issue with the way that proportional reclaim
> worked previously -- it promotes having no memory.low, since it makes
> pressure higher during low reclaim. This happens because we base our
> scan pressure modulation on how far memory.current is between memory.min
> and memory.low, but if memory.low is unset, we only use the overage
> method. In most cromulent configurations, this then means that we end up
> with *more* pressure than with no memory.low at all when we're in low
> reclaim, which is not really very usable or expected.
> With this patch, memory.low and memory.min affect reclaim pressure in a
> more understandable and composable way. For example, from a user
> standpoint, "protected" memory now remains untouchable from a reclaim
> aggression standpoint, and users can also have more confidence that
> bursty workloads will still receive some amount of guaranteed
> protection.
> Signed-off-by: Chris Down <>
> Reviewed-by: Roman Gushchin <>
> Cc: Johannes Weiner <>
> Cc: Andrew Morton <>
> Cc: Michal Hocko <>
> Cc: Tejun Heo <>
> Cc: Roman Gushchin <>
> Cc: Dennis Zhou <>
> Cc:
> Cc:
> Cc:
> Cc:

Acked-by: Johannes Weiner <>

 \ /
  Last update: 2019-07-16 19:12    [W:0.230 / U:37.728 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site