From: Michel Lespinasse <walken@google.com> To: Jan Kara <jack@suse.cz> Cc: LKML <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/6] lib: Implement range locks Date: Mon, 11 Feb 2013 03:03:30 -0800 [thread overview] Message-ID: <CANN689G8f2QuROecapFcbcNUggGWv9bTuHSV+k4KBLj=_E7uFg@mail.gmail.com> (raw) In-Reply-To: <20130211102730.GA5318@quack.suse.cz> On Mon, Feb 11, 2013 at 2:27 AM, Jan Kara <jack@suse.cz> wrote: > On Sun 10-02-13 21:42:32, Michel Lespinasse wrote: >> On Thu, Jan 31, 2013 at 1:49 PM, Jan Kara <jack@suse.cz> wrote: >> > +void range_lock_init(struct range_lock *lock, unsigned long start, >> > + unsigned long end); >> > +void range_lock(struct range_lock_tree *tree, struct range_lock *lock); >> > +void range_unlock(struct range_lock_tree *tree, struct range_lock *lock); >> >> Is there a point to separating the init and lock stages ? maybe the API could be >> void range_lock(struct range_lock_tree *tree, struct range_lock *lock, >> unsigned long start, unsigned long last); >> void range_unlock(struct range_lock_tree *tree, struct range_lock *lock); > I was thinking about this as well. Currently I don't have a place which > would make it beneficial to separate _init and _lock but I can imagine such > uses (where you don't want to pass the interval information down the stack > and it's easier to pass the whole lock structure). Also it looks a bit > confusing to pass (tree, lock, start, last) to the locking functon. So I > left it there. > > OTOH I had to somewhat change the API so that the locking phase is now > separated in "lock_prep" phase which inserts the node into the tree and > counts blocking ranges and "wait" phase which waits for the blocking ranges > to unlock. The reason for this split is that while "lock_prep" needs to > happen under some lock synchronizing operations on the tree, "wait" phase > can be easily lockless. So this allows me to remove the knowledge of how > operations on the tree are synchronized from range locking code itself. > That further allowed me to use mapping->tree_lock for synchronization and > basically reduce the cost of mapping range locking close to 0 for buffered > IO (just a single tree lookup in the tree in the fast path). Ah yes, being able to externalize the lock is good. I think in this case, it makes the most sense for lock_prep phase to also initialize the lock node, though. >> Reviewed-by: Michel Lespinasse <walken@google.com> > I actually didn't add this because there are some differences in the > current version... Did I miss another posting of yours, or is that coming up ? Cheers, -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies.
WARNING: multiple messages have this Message-ID (diff)
From: Michel Lespinasse <walken@google.com> To: Jan Kara <jack@suse.cz> Cc: LKML <linux-kernel@vger.kernel.org>, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/6] lib: Implement range locks Date: Mon, 11 Feb 2013 03:03:30 -0800 [thread overview] Message-ID: <CANN689G8f2QuROecapFcbcNUggGWv9bTuHSV+k4KBLj=_E7uFg@mail.gmail.com> (raw) In-Reply-To: <20130211102730.GA5318@quack.suse.cz> On Mon, Feb 11, 2013 at 2:27 AM, Jan Kara <jack@suse.cz> wrote: > On Sun 10-02-13 21:42:32, Michel Lespinasse wrote: >> On Thu, Jan 31, 2013 at 1:49 PM, Jan Kara <jack@suse.cz> wrote: >> > +void range_lock_init(struct range_lock *lock, unsigned long start, >> > + unsigned long end); >> > +void range_lock(struct range_lock_tree *tree, struct range_lock *lock); >> > +void range_unlock(struct range_lock_tree *tree, struct range_lock *lock); >> >> Is there a point to separating the init and lock stages ? maybe the API could be >> void range_lock(struct range_lock_tree *tree, struct range_lock *lock, >> unsigned long start, unsigned long last); >> void range_unlock(struct range_lock_tree *tree, struct range_lock *lock); > I was thinking about this as well. Currently I don't have a place which > would make it beneficial to separate _init and _lock but I can imagine such > uses (where you don't want to pass the interval information down the stack > and it's easier to pass the whole lock structure). Also it looks a bit > confusing to pass (tree, lock, start, last) to the locking functon. So I > left it there. > > OTOH I had to somewhat change the API so that the locking phase is now > separated in "lock_prep" phase which inserts the node into the tree and > counts blocking ranges and "wait" phase which waits for the blocking ranges > to unlock. The reason for this split is that while "lock_prep" needs to > happen under some lock synchronizing operations on the tree, "wait" phase > can be easily lockless. So this allows me to remove the knowledge of how > operations on the tree are synchronized from range locking code itself. > That further allowed me to use mapping->tree_lock for synchronization and > basically reduce the cost of mapping range locking close to 0 for buffered > IO (just a single tree lookup in the tree in the fast path). Ah yes, being able to externalize the lock is good. I think in this case, it makes the most sense for lock_prep phase to also initialize the lock node, though. >> Reviewed-by: Michel Lespinasse <walken@google.com> > I actually didn't add this because there are some differences in the > current version... Did I miss another posting of yours, or is that coming up ? Cheers, -- Michel "Walken" Lespinasse A program is never fully debugged until the last user dies. -- 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:[~2013-02-11 11:03 UTC|newest] Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-01-31 21:49 [PATCH 0/6 RFC] Mapping range lock Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 1/6] lib: Implement range locks Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 23:57 ` Andrew Morton 2013-01-31 23:57 ` Andrew Morton 2013-02-04 16:41 ` Jan Kara 2013-02-04 16:41 ` Jan Kara 2013-02-11 5:42 ` Michel Lespinasse 2013-02-11 5:42 ` Michel Lespinasse 2013-02-11 10:27 ` Jan Kara 2013-02-11 10:27 ` Jan Kara 2013-02-11 11:03 ` Michel Lespinasse [this message] 2013-02-11 11:03 ` Michel Lespinasse 2013-02-11 12:58 ` Jan Kara 2013-02-11 12:58 ` Jan Kara 2013-01-31 21:49 ` [PATCH 2/6] fs: Take mapping lock in generic read paths Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 23:59 ` Andrew Morton 2013-01-31 23:59 ` Andrew Morton 2013-02-04 12:47 ` Jan Kara 2013-02-04 12:47 ` Jan Kara 2013-02-08 14:59 ` Jan Kara 2013-02-08 14:59 ` Jan Kara 2013-01-31 21:49 ` [PATCH 3/6] fs: Provide function to take mapping lock in buffered write path Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 4/6] fs: Don't call dio_cleanup() before submitting all bios Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 5/6] fs: Take mapping lock during direct IO Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-01-31 21:49 ` [PATCH 6/6] ext3: Convert ext3 to use mapping lock Jan Kara 2013-01-31 21:49 ` Jan Kara 2013-02-01 0:07 ` [PATCH 0/6 RFC] Mapping range lock Andrew Morton 2013-02-01 0:07 ` Andrew Morton 2013-02-04 9:29 ` Zheng Liu 2013-02-04 9:29 ` Zheng Liu 2013-02-04 12:38 ` Jan Kara 2013-02-04 12:38 ` Jan Kara 2013-02-05 23:25 ` Dave Chinner 2013-02-05 23:25 ` Dave Chinner 2013-02-06 19:25 ` Jan Kara 2013-02-06 19:25 ` Jan Kara 2013-02-07 2:43 ` Dave Chinner 2013-02-07 2:43 ` Dave Chinner 2013-02-07 11:06 ` Jan Kara 2013-02-07 11:06 ` Jan Kara
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