From: Uladzislau Rezki <urezki@gmail.com>
To: Baoquan He <bhe@redhat.com>
Cc: Uladzislau Rezki <urezki@gmail.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Dave Chinner <david@fromorbit.com>,
"Paul E . McKenney" <paulmck@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Subject: Re: [PATCH v2 6/9] mm: vmalloc: Offload free_vmap_area_lock lock
Date: Thu, 7 Sep 2023 11:33:43 +0200 [thread overview]
Message-ID: <ZPmY98hbAo+/Lcf4@pc636> (raw)
In-Reply-To: <ZPkT8RJJgY0HGwmC@MiWiFi-R3L-srv>
On Thu, Sep 07, 2023 at 08:06:09AM +0800, Baoquan He wrote:
> On 09/06/23 at 09:16pm, Uladzislau Rezki wrote:
> > > > static void free_vmap_area(struct vmap_area *va)
> > > > {
> > > > struct vmap_node *vn = addr_to_node(va->va_start);
> > > > + int vn_id = decode_vn_id(va->flags);
> > > >
> > > > /*
> > > > * Remove from the busy tree/list.
> > > > @@ -1594,12 +1629,19 @@ static void free_vmap_area(struct vmap_area *va)
> > > > unlink_va(va, &vn->busy.root);
> > > > spin_unlock(&vn->busy.lock);
> > > >
> > > > - /*
> > > > - * Insert/Merge it back to the free tree/list.
> > > > - */
> > > > - spin_lock(&free_vmap_area_lock);
> > > > - merge_or_add_vmap_area_augment(va, &free_vmap_area_root, &free_vmap_area_list);
> > > > - spin_unlock(&free_vmap_area_lock);
> > > > + if (vn_id >= 0) {
> > >
> > > In alloc_vmap_area(), the vn_id is encoded into va->flags. When
> > > allocation failed, the vn_id = 0. Here should we change to check 'if
> > > (vn_id > 0)' becasue the vn_id == 0 means no available vn_id encoded
> > > into. And I do not get how we treat the case vn_id truly is 0.
> > >
> > > va->flags = (addr != vend) ? encode_vn_id(vn_id) : 0;
> > >
> > Yes, vn_id always >= 0, so it is positive since it is an index.
> > We encode a vn_id as vn_id + 1. For example if it is zero we write 1.
> >
> > If not node allocation path or an error zero is written. Decoding
> > is done as: zero - 1 = -1, so it is negative value, i.e. decode_vn_id()
> > function returns -1.
>
> Ah, I see it now, thanks. It would be helpful to add some explanation
> above decode_vn_id() lest people misunderstand this like me?
>
I got that feeling also. This makes sense, so i will comment it!
--
Uladzislau Rezki
next prev parent reply other threads:[~2023-09-07 9:33 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-29 8:11 [PATCH v2 0/9] Mitigate a vmap lock contention v2 Uladzislau Rezki (Sony)
2023-08-29 8:11 ` [PATCH v2 1/9] mm: vmalloc: Add va_alloc() helper Uladzislau Rezki (Sony)
2023-09-06 5:51 ` Baoquan He
2023-09-06 15:06 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 2/9] mm: vmalloc: Rename adjust_va_to_fit_type() function Uladzislau Rezki (Sony)
2023-09-06 5:51 ` Baoquan He
2023-09-06 16:27 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 3/9] mm: vmalloc: Move vmap_init_free_space() down in vmalloc.c Uladzislau Rezki (Sony)
2023-09-06 5:52 ` Baoquan He
2023-09-06 16:29 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 4/9] mm: vmalloc: Remove global vmap_area_root rb-tree Uladzislau Rezki (Sony)
2023-08-29 14:30 ` kernel test robot
2023-08-30 14:48 ` Uladzislau Rezki
2023-09-07 2:17 ` Baoquan He
2023-09-07 9:38 ` Baoquan He
2023-09-07 9:40 ` Uladzislau Rezki
2023-09-07 9:39 ` Uladzislau Rezki
2023-09-07 9:58 ` Baoquan He
2023-09-08 1:51 ` HAGIO KAZUHITO(萩尾 一仁)
2023-09-08 4:43 ` Baoquan He
2023-09-08 5:01 ` HAGIO KAZUHITO(萩尾 一仁)
2023-09-08 6:44 ` Baoquan He
2023-09-08 11:25 ` Uladzislau Rezki
2023-09-08 11:38 ` Baoquan He
2023-09-08 13:23 ` Uladzislau Rezki
2023-09-11 2:38 ` Baoquan He
2023-09-11 16:53 ` Uladzislau Rezki
2023-09-12 13:19 ` Baoquan He
2023-08-29 8:11 ` [PATCH v2 5/9] mm: vmalloc: Remove global purge_vmap_area_root rb-tree Uladzislau Rezki (Sony)
2023-09-11 2:57 ` Baoquan He
2023-09-11 17:00 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 6/9] mm: vmalloc: Offload free_vmap_area_lock lock Uladzislau Rezki (Sony)
2023-09-06 6:04 ` Baoquan He
2023-09-06 19:16 ` Uladzislau Rezki
2023-09-07 0:06 ` Baoquan He
2023-09-07 9:33 ` Uladzislau Rezki [this message]
2023-09-11 3:25 ` Baoquan He
2023-09-11 17:10 ` Uladzislau Rezki
2023-09-12 13:21 ` Baoquan He
2023-08-29 8:11 ` [PATCH v2 7/9] mm: vmalloc: Support multiple nodes in vread_iter Uladzislau Rezki (Sony)
2023-09-11 3:58 ` Baoquan He
2023-09-11 18:16 ` Uladzislau Rezki
2023-09-12 13:42 ` Baoquan He
2023-09-13 15:42 ` Uladzislau Rezki
2023-09-14 3:02 ` Baoquan He
2023-09-14 3:36 ` Baoquan He
2023-09-14 3:38 ` Baoquan He
2023-09-13 10:59 ` Baoquan He
2023-09-13 15:38 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 8/9] mm: vmalloc: Support multiple nodes in vmallocinfo Uladzislau Rezki (Sony)
2023-09-15 13:02 ` Baoquan He
2023-09-15 18:32 ` Uladzislau Rezki
2023-08-29 8:11 ` [PATCH v2 9/9] mm: vmalloc: Set nr_nodes/node_size based on CPU-cores Uladzislau Rezki (Sony)
2023-09-15 13:03 ` Baoquan He
2023-09-15 18:31 ` Uladzislau Rezki
2023-08-31 1:15 ` [PATCH v2 0/9] Mitigate a vmap lock contention v2 Baoquan He
2023-08-31 16:26 ` Uladzislau Rezki
2023-09-04 14:55 ` Uladzislau Rezki
2023-09-04 19:53 ` Andrew Morton
2023-09-05 6:53 ` Uladzislau Rezki
2023-09-06 20:04 ` Lorenzo Stoakes
2023-09-07 9:15 ` Uladzislau Rezki
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=ZPmY98hbAo+/Lcf4@pc636 \
--to=urezki@gmail.com \
--cc=Liam.Howlett@oracle.com \
--cc=akpm@linux-foundation.org \
--cc=bhe@redhat.com \
--cc=david@fromorbit.com \
--cc=hch@infradead.org \
--cc=joel@joelfernandes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=lstoakes@gmail.com \
--cc=oleksiy.avramchenko@sony.com \
--cc=paulmck@kernel.org \
--cc=willy@infradead.org \
/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).