From: Dennis Zhou <dennis@kernel.org>
To: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/6] percpu: split __pcpu_balance_workfn()
Date: Fri, 16 Apr 2021 21:06:57 +0000 [thread overview]
Message-ID: <YHn8cURoctyYV5LT@google.com> (raw)
In-Reply-To: <20210408035736.883861-3-guro@fb.com>
Hello,
On Wed, Apr 07, 2021 at 08:57:32PM -0700, Roman Gushchin wrote:
> __pcpu_balance_workfn() became fairly big and hard to follow, but in
> fact it consists of two fully independent parts, responsible for
> the destruction of excessive free chunks and population of necessarily
> amount of free pages.
>
> In order to simplify the code and prepare for adding of a new
> functionality, split it in two functions:
>
> 1) pcpu_balance_free,
> 2) pcpu_balance_populated.
>
> Move the taking/releasing of the pcpu_alloc_mutex to an upper level
> to keep the current synchronization in place.
>
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Reviewed-by: Dennis Zhou <dennis@kernel.org>
> ---
> mm/percpu.c | 46 +++++++++++++++++++++++++++++-----------------
> 1 file changed, 29 insertions(+), 17 deletions(-)
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 2f27123bb489..7e31e1b8725f 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -1933,31 +1933,22 @@ void __percpu *__alloc_reserved_percpu(size_t size, size_t align)
> }
>
> /**
> - * __pcpu_balance_workfn - manage the amount of free chunks and populated pages
> + * pcpu_balance_free - manage the amount of free chunks
> * @type: chunk type
> *
> - * Reclaim all fully free chunks except for the first one. This is also
> - * responsible for maintaining the pool of empty populated pages. However,
> - * it is possible that this is called when physical memory is scarce causing
> - * OOM killer to be triggered. We should avoid doing so until an actual
> - * allocation causes the failure as it is possible that requests can be
> - * serviced from already backed regions.
> + * Reclaim all fully free chunks except for the first one.
> */
> -static void __pcpu_balance_workfn(enum pcpu_chunk_type type)
> +static void pcpu_balance_free(enum pcpu_chunk_type type)
> {
> - /* gfp flags passed to underlying allocators */
> - const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
> LIST_HEAD(to_free);
> struct list_head *pcpu_slot = pcpu_chunk_list(type);
> struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1];
> struct pcpu_chunk *chunk, *next;
> - int slot, nr_to_pop, ret;
>
> /*
> * There's no reason to keep around multiple unused chunks and VM
> * areas can be scarce. Destroy all free chunks except for one.
> */
> - mutex_lock(&pcpu_alloc_mutex);
> spin_lock_irq(&pcpu_lock);
>
> list_for_each_entry_safe(chunk, next, free_head, list) {
> @@ -1985,6 +1976,25 @@ static void __pcpu_balance_workfn(enum pcpu_chunk_type type)
> pcpu_destroy_chunk(chunk);
> cond_resched();
> }
> +}
> +
> +/**
> + * pcpu_balance_populated - manage the amount of populated pages
> + * @type: chunk type
> + *
> + * Maintain a certain amount of populated pages to satisfy atomic allocations.
> + * It is possible that this is called when physical memory is scarce causing
> + * OOM killer to be triggered. We should avoid doing so until an actual
> + * allocation causes the failure as it is possible that requests can be
> + * serviced from already backed regions.
> + */
> +static void pcpu_balance_populated(enum pcpu_chunk_type type)
> +{
> + /* gfp flags passed to underlying allocators */
> + const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
> + struct list_head *pcpu_slot = pcpu_chunk_list(type);
> + struct pcpu_chunk *chunk;
> + int slot, nr_to_pop, ret;
>
> /*
> * Ensure there are certain number of free populated pages for
> @@ -2054,22 +2064,24 @@ static void __pcpu_balance_workfn(enum pcpu_chunk_type type)
> goto retry_pop;
> }
> }
> -
> - mutex_unlock(&pcpu_alloc_mutex);
> }
>
> /**
> * pcpu_balance_workfn - manage the amount of free chunks and populated pages
> * @work: unused
> *
> - * Call __pcpu_balance_workfn() for each chunk type.
> + * Call pcpu_balance_free() and pcpu_balance_populated() for each chunk type.
> */
> static void pcpu_balance_workfn(struct work_struct *work)
> {
> enum pcpu_chunk_type type;
>
> - for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
> - __pcpu_balance_workfn(type);
> + for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) {
> + mutex_lock(&pcpu_alloc_mutex);
> + pcpu_balance_free(type);
> + pcpu_balance_populated(type);
> + mutex_unlock(&pcpu_alloc_mutex);
> + }
> }
>
> /**
> --
> 2.30.2
>
>
I've applied this to for-5.14.
Thanks,
Dennis
next prev parent reply other threads:[~2021-04-16 21:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-08 3:57 [PATCH v3 0/6] percpu: partial chunk depopulation Roman Gushchin
2021-04-08 3:57 ` [PATCH v3 1/6] percpu: fix a comment about the chunks ordering Roman Gushchin
2021-04-16 21:06 ` Dennis Zhou
2021-04-08 3:57 ` [PATCH v3 2/6] percpu: split __pcpu_balance_workfn() Roman Gushchin
2021-04-16 21:06 ` Dennis Zhou [this message]
2021-04-08 3:57 ` [PATCH v3 3/6] percpu: make pcpu_nr_empty_pop_pages per chunk type Roman Gushchin
2021-04-16 21:08 ` Dennis Zhou
2021-04-08 3:57 ` [PATCH v3 4/6] percpu: generalize pcpu_balance_populated() Roman Gushchin
2021-04-16 21:09 ` Dennis Zhou
2021-04-08 3:57 ` [PATCH v3 5/6] percpu: factor out pcpu_check_chunk_hint() Roman Gushchin
2021-04-16 21:15 ` Dennis Zhou
2021-04-08 3:57 ` [PATCH v3 6/6] percpu: implement partial chunk depopulation Roman Gushchin
2021-04-16 12:56 ` [PATCH v3 0/6] percpu: " Pratik Sampat
2021-04-16 14:18 ` Dennis Zhou
2021-04-16 15:28 ` Pratik Sampat
2021-04-16 17:13 ` Roman Gushchin
2021-04-16 18:27 ` Pratik Sampat
2021-04-16 18:34 ` Roman Gushchin
2021-04-16 18:41 ` Pratik Sampat
2021-04-16 19:09 ` Roman Gushchin
2021-04-16 19:44 ` Pratik Sampat
2021-04-16 20:03 ` Roman Gushchin
2021-04-17 7:08 ` Pratik Sampat
2021-04-16 21:47 ` Dennis Zhou
2021-04-17 7:14 ` Pratik Sampat
2021-04-16 16:21 ` Roman Gushchin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YHn8cURoctyYV5LT@google.com \
--to=dennis@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=guro@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=tj@kernel.org \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).