From: "J. Bruce Fields" <email@example.com> To: NeilBrown <firstname.lastname@example.org> Cc: Jeff Layton <email@example.com>, Alexander Viro <firstname.lastname@example.org>, Martin Wilck <email@example.com>, firstname.lastname@example.org, Frank Filz <email@example.com>, firstname.lastname@example.org Subject: Re: [PATCH 0/5 - V2] locks: avoid thundering-herd wake-ups Date: Fri, 10 Aug 2018 11:47:42 -0400 Message-ID: <20180810154742.GE7906@fieldses.org> (raw) In-Reply-To: <email@example.com> On Fri, Aug 10, 2018 at 01:17:14PM +1000, NeilBrown wrote: > On Thu, Aug 09 2018, J. Bruce Fields wrote: > > > On Fri, Aug 10, 2018 at 11:50:58AM +1000, NeilBrown wrote: > >> You're good at this game! > > > > Everybody's got to have a hobby, mine is pathological posix locking > > cases.... > > > >> So, because a locker with the same "owner" gets a free pass, you can > >> *never* say that any lock which conflicts with A also conflicts with B, > >> as a lock with the same owner as B will never conflict with B, even > >> though it conflicts with A. > >> > >> I think there is still value in having the tree, but when a waiter is > >> attached under a new blocker, we need to walk the whole tree beneath the > >> waiter and detach/wake anything that is not blocked by the new blocker. > > > > If you're walking the whole tree every time then it might as well be a > > flat list, I think? > > The advantage of a tree is that it keeps over-lapping locks closer > together. > For it to make a difference you would need a load where lots of threads > were locking several different small ranges, and other threads were > locking large ranges that cover all the small ranges. OK, I'm not sure I understand, but I'll give another look at the next version.... > I doubt this is common, but it doesn't seem as strange as other things > I've seen in the wild. > The other advantage, of course, is that I've already written the code, > and I like it. > > Maybe I'll do a simple-list version, then a patch to convert that to the > clever-tree version, and we can then have something concrete to assess. That might help, thanks. --b.
next prev parent reply index Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-08-09 2:04 NeilBrown 2018-08-09 2:04 ` [PATCH 1/5] fs/locks: rename some lists and pointers NeilBrown 2018-08-09 2:04 ` [PATCH 2/5] fs/locks: allow a lock request to block other requests NeilBrown 2018-08-09 2:04 ` [PATCH 3/5] fs/locks: change all *_conflict() functions to return a new enum NeilBrown 2018-08-09 11:09 ` Jeff Layton 2018-08-09 13:09 ` J. Bruce Fields 2018-08-09 23:40 ` NeilBrown 2018-08-10 0:56 ` J. Bruce Fields 2018-08-09 2:04 ` [PATCH 4/5] fs/locks: split out __locks_wake_one() NeilBrown 2018-08-09 2:04 ` [PATCH 5/5] fs/locks: create a tree of dependent requests NeilBrown 2018-08-09 11:17 ` Jeff Layton 2018-08-09 23:25 ` NeilBrown 2018-08-09 14:13 ` J. Bruce Fields 2018-08-09 22:19 ` NeilBrown 2018-08-10 0:36 ` J. Bruce Fields 2018-08-09 17:32 ` [PATCH 0/5 - V2] locks: avoid thundering-herd wake-ups J. Bruce Fields 2018-08-09 22:12 ` NeilBrown 2018-08-10 0:29 ` J. Bruce Fields 2018-08-10 1:50 ` NeilBrown 2018-08-10 2:52 ` J. Bruce Fields 2018-08-10 3:17 ` NeilBrown 2018-08-10 15:47 ` J. Bruce Fields [this message] 2018-08-11 11:56 ` Jeff Layton 2018-08-11 12:35 ` J. Bruce Fields 2018-08-11 11:51 ` Jeff Layton 2018-08-11 12:21 ` J. Bruce Fields 2018-08-11 13:15 ` Jeff Layton
Reply instructions: You may reply publically 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=20180810154742.GE7906@fieldses.org \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.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
LKML Archive on lore.kernel.org Archives are clonable: git clone --mirror https://lore.kernel.org/lkml/0 lkml/git/0.git git clone --mirror https://lore.kernel.org/lkml/1 lkml/git/1.git git clone --mirror https://lore.kernel.org/lkml/2 lkml/git/2.git git clone --mirror https://lore.kernel.org/lkml/3 lkml/git/3.git git clone --mirror https://lore.kernel.org/lkml/4 lkml/git/4.git git clone --mirror https://lore.kernel.org/lkml/5 lkml/git/5.git git clone --mirror https://lore.kernel.org/lkml/6 lkml/git/6.git git clone --mirror https://lore.kernel.org/lkml/7 lkml/git/7.git # If you have public-inbox 1.1+ installed, you may # initialize and index your mirror using the following commands: public-inbox-init -V2 lkml lkml/ https://lore.kernel.org/lkml \ firstname.lastname@example.org email@example.com public-inbox-index lkml Newsgroup available over NNTP: nntp://nntp.lore.kernel.org/org.kernel.vger.linux-kernel AGPL code for this site: git clone https://public-inbox.org/ public-inbox