From: Jakub Kicinski <firstname.lastname@example.org> To: Shakeel Butt <email@example.com> Cc: Andrew Morton <firstname.lastname@example.org>, Linux MM <email@example.com>, Kernel Team <firstname.lastname@example.org>, Tejun Heo <email@example.com>, Johannes Weiner <firstname.lastname@example.org>, Chris Down <email@example.com>, Cgroups <firstname.lastname@example.org>, Michal Hocko <email@example.com> Subject: Re: [PATCH mm v3 3/3] mm: automatically penalize tasks with high swap use Date: Mon, 18 May 2020 12:42:10 -0700 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <CALvZod5Dcee8CaNfkhQQbvC1OuOTO7qE9bJw9NAa8nd2Cru6hA@mail.gmail.com> On Sun, 17 May 2020 06:44:52 -0700 Shakeel Butt wrote: > > Use one counter for number of pages allocated under pressure > > to save struct task space and avoid two separate hierarchy > > walks on the hot path. > > The above para seems out of place. It took some time to realize you > are talking about current->memcg_nr_pages_over_high. IMO instead of > this para, a comment in code would be much better. Where would you like to see the comment? In struct task or where counter is bumped? > > Take the new high limit into account when determining if swap > > is "full". Borrowing the explanation from Johannes: > > > > The idea behind "swap full" is that as long as the workload has plenty > > of swap space available and it's not changing its memory contents, it > > makes sense to generously hold on to copies of data in the swap > > device, even after the swapin. A later reclaim cycle can drop the page > > without any IO. Trading disk space for IO. > > > > But the only two ways to reclaim a swap slot is when they're faulted > > in and the references go away, or by scanning the virtual address space > > like swapoff does - which is very expensive (one could argue it's too > > expensive even for swapoff, it's often more practical to just reboot). > > > > So at some point in the fill level, we have to start freeing up swap > > slots on fault/swapin. > > swap.high allows the user to force the kernel to start freeing swap > slots before half-full heuristic, right? I'd say that the definition of full is extended to include swap.high.
next prev parent reply other threads:[~2020-05-18 19:42 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-15 20:20 [PATCH mm v3 0/3] memcg: Slow down swap allocation as the available space gets depleted Jakub Kicinski 2020-05-15 20:20 ` [PATCH mm v3 1/3] mm: prepare for swap over-high accounting and penalty calculation Jakub Kicinski 2020-05-15 20:20 ` [PATCH mm v3 2/3] mm: move penalty delay clamping out of calculate_high_delay() Jakub Kicinski 2020-05-15 20:20 ` [PATCH mm v3 3/3] mm: automatically penalize tasks with high swap use Jakub Kicinski 2020-05-17 13:44 ` Shakeel Butt 2020-05-18 19:42 ` Jakub Kicinski [this message] 2020-05-18 19:58 ` Shakeel Butt 2020-05-19 0:42 ` Jakub Kicinski 2020-05-19 1:10 ` Shakeel Butt
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