From: "Huang\, Ying" <ying.huang@intel.com>
To: Andrea Righi <andrea.righi@canonical.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan@kernel.org>,
Anchal Agarwal <anchalag@amazon.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] mm: swap: use fixed-size readahead during swapoff
Date: Mon, 13 Apr 2020 21:13:33 +0800 [thread overview]
Message-ID: <875ze37cle.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20200413111810.GA801367@xps-13> (Andrea Righi's message of "Mon, 13 Apr 2020 13:18:10 +0200")
Andrea Righi <andrea.righi@canonical.com> writes:
> The global swap-in readahead policy takes in account the previous access
> patterns, using a scaling heuristic to determine the optimal readahead
> chunk dynamically.
>
> This works pretty well in most cases, but like any heuristic there are
> specific cases when this approach is not ideal, for example the swapoff
> scenario.
>
> During swapoff we just want to load back into memory all the swapped-out
> pages and for this specific use case a fixed-size readahead is more
> efficient.
>
> The specific use case this patch is addressing is to improve swapoff
> performance when a VM has been hibernated, resumed and all memory needs
> to be forced back to RAM by disabling swap (see the test case below).
Why do you need to swapoff after resuming? The swap device isn't used
except hibernation? I guess the process is,
1) add swap device to VM
2) hibernate
3) resume
4) swapoff
Some pages are swapped out in step 2? If os, can we just set
/proc/sys/vm/swappiness to 0 to avoid swapping in step 2?
Best Regards,
Huang, Ying
next prev parent reply other threads:[~2020-04-13 13:13 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 11:18 [PATCH v2] mm: swap: use fixed-size readahead during swapoff Andrea Righi
2020-04-13 13:00 ` Huang, Ying
2020-04-13 13:00 ` Huang, Ying
2020-04-13 13:31 ` Andrea Righi
2020-04-14 1:31 ` Huang, Ying
2020-04-14 1:31 ` Huang, Ying
2020-04-14 13:05 ` Andrea Righi
2020-04-15 2:37 ` Huang, Ying
2020-04-15 2:37 ` Huang, Ying
2020-04-15 7:32 ` Andrea Righi
2020-04-15 7:44 ` Huang, Ying
2020-04-15 7:44 ` Huang, Ying
2020-04-15 9:19 ` Andrea Righi
2020-04-16 0:44 ` Huang, Ying
2020-04-16 0:44 ` Huang, Ying
2020-04-15 12:00 ` Andrea Righi
2020-04-16 0:41 ` Huang, Ying
2020-04-16 0:41 ` Huang, Ying
2020-04-16 17:21 ` Andrea Righi
2020-04-13 13:13 ` Huang, Ying [this message]
2020-04-13 13:13 ` Huang, Ying
2020-04-13 13:26 ` Andrea Righi
2020-04-14 1:45 ` Huang, Ying
2020-04-14 1:45 ` Huang, Ying
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