From: Michal Hocko <mhocko@kernel.org>
To: Wei Wang <wei.w.wang@intel.com>
Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org,
qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org,
kvm@vger.kernel.org, linux-mm@kvack.org, mst@redhat.com,
akpm@linux-foundation.org, mawilcox@microsoft.com,
david@redhat.com, cornelia.huck@de.ibm.com,
mgorman@techsingularity.net, aarcange@redhat.com,
amit.shah@redhat.com, pbonzini@redhat.com, willy@infradead.org,
liliang.opensource@gmail.com, yang.zhang.wz@gmail.com,
quan.xu@aliyun.com
Subject: Re: [PATCH v15 4/5] mm: support reporting free page blocks
Date: Mon, 28 Aug 2017 15:33:26 +0200 [thread overview]
Message-ID: <20170828133326.GN17097@dhcp22.suse.cz> (raw)
In-Reply-To: <1503914913-28893-5-git-send-email-wei.w.wang@intel.com>
On Mon 28-08-17 18:08:32, Wei Wang wrote:
> This patch adds support to walk through the free page blocks in the
> system and report them via a callback function. Some page blocks may
> leave the free list after zone->lock is released, so it is the caller's
> responsibility to either detect or prevent the use of such pages.
>
> One use example of this patch is to accelerate live migration by skipping
> the transfer of free pages reported from the guest. A popular method used
> by the hypervisor to track which part of memory is written during live
> migration is to write-protect all the guest memory. So, those pages that
> are reported as free pages but are written after the report function
> returns will be captured by the hypervisor, and they will be added to the
> next round of memory transfer.
OK, looks much better. I still have few nits.
> +extern void walk_free_mem_block(void *opaque,
> + int min_order,
> + bool (*report_page_block)(void *, unsigned long,
> + unsigned long));
> +
please add names to arguments of the prototype
> /*
> * Free reserved pages within range [PAGE_ALIGN(start), end & PAGE_MASK)
> * into the buddy system. The freed pages will be poisoned with pattern
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 6d00f74..81eedc7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4762,6 +4762,71 @@ void show_free_areas(unsigned int filter, nodemask_t *nodemask)
> show_swap_cache_info();
> }
>
> +/**
> + * walk_free_mem_block - Walk through the free page blocks in the system
> + * @opaque: the context passed from the caller
> + * @min_order: the minimum order of free lists to check
> + * @report_page_block: the callback function to report free page blocks
page_block has meaning in the core MM which doesn't strictly match its
usage here. Moreover we are reporting pfn ranges rather than struct page
range. So report_pfn_range would suit better.
[...]
> + for_each_populated_zone(zone) {
> + for (order = MAX_ORDER - 1; order >= min_order; order--) {
> + for (mt = 0; !stop && mt < MIGRATE_TYPES; mt++) {
> + spin_lock_irqsave(&zone->lock, flags);
> + list = &zone->free_area[order].free_list[mt];
> + list_for_each_entry(page, list, lru) {
> + pfn = page_to_pfn(page);
> + stop = report_page_block(opaque, pfn,
> + 1 << order);
> + if (stop)
> + break;
if (stop) {
spin_unlock_irqrestore(&zone->lock, flags);
return;
}
would be both easier and less error prone. E.g. You wouldn't pointlessly
iterate over remaining orders just to realize there is nothing to be
done for those...
> + }
> + spin_unlock_irqrestore(&zone->lock, flags);
> + }
> + }
> + }
> +}
> +EXPORT_SYMBOL_GPL(walk_free_mem_block);
--
Michal Hocko
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-08-28 13:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-28 10:08 [PATCH v15 0/5] Virtio-balloon Enhancement Wei Wang
2017-08-28 10:08 ` [PATCH v15 1/5] lib/xbitmap: Introduce xbitmap Wei Wang
2017-09-11 12:54 ` Matthew Wilcox
2017-09-12 13:23 ` Wei Wang
2017-08-28 10:08 ` [PATCH v15 2/5] lib/xbitmap: add xb_find_next_bit() and xb_zero() Wei Wang
2017-09-11 13:27 ` Matthew Wilcox
2017-09-30 4:24 ` Wang, Wei W
2017-08-28 10:08 ` [PATCH v15 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG Wei Wang
2017-08-28 18:03 ` Michael S. Tsirkin
2017-08-29 3:09 ` Wei Wang
2017-09-08 3:36 ` Michael S. Tsirkin
2017-09-08 11:09 ` [virtio-dev] " Wei Wang
2017-09-29 4:01 ` Michael S. Tsirkin
2017-09-29 6:55 ` Wei Wang
2017-08-28 10:08 ` [PATCH v15 4/5] mm: support reporting free page blocks Wei Wang
2017-08-28 13:33 ` Michal Hocko [this message]
2017-08-28 14:09 ` Michal Hocko
2017-08-29 3:23 ` Wei Wang
2017-08-28 10:08 ` [PATCH v15 5/5] virtio-balloon: VIRTIO_BALLOON_F_CTRL_VQ Wei Wang
2017-09-05 11:57 ` Wang, Wei W
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=20170828133326.GN17097@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=amit.shah@redhat.com \
--cc=cornelia.huck@de.ibm.com \
--cc=david@redhat.com \
--cc=kvm@vger.kernel.org \
--cc=liliang.opensource@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mawilcox@microsoft.com \
--cc=mgorman@techsingularity.net \
--cc=mst@redhat.com \
--cc=pbonzini@redhat.com \
--cc=qemu-devel@nongnu.org \
--cc=quan.xu@aliyun.com \
--cc=virtio-dev@lists.oasis-open.org \
--cc=virtualization@lists.linux-foundation.org \
--cc=wei.w.wang@intel.com \
--cc=willy@infradead.org \
--cc=yang.zhang.wz@gmail.com \
/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).