svn commit: r292299 - head/sys/kern

[Adrian Chadd]

On 16 December 2015 at 00:01, Konstantin Belousov <kostikbel at gmail.com> wrote:
> On Wed, Dec 16, 2015 at 12:13:16AM +0000, Adrian Chadd wrote:
>> Author: adrian
>> Date: Wed Dec 16 00:13:16 2015
>> New Revision: 292299
>> URL: https://svnweb.freebsd.org/changeset/base/292299
>>
>> Log:
>>   Don't call wakeup if we're just returning reserved space; just
>>   return the reservation and wait for more space to appear.
> Issue which is supposedly fixed by the commit is not due to the possibly
> excessive wakeups. bufspace_release() and bufspace_wakeup() clear
> the needsbuffer variable, while the code flow in getnewbuf() calls
> bufspace_wait() to wait for the condition, which prevented the buffer
> allocation from succeeding, to pass.

Right. There's still some more work to do there to chase issues down
so I can remove that sched_yield() workaround I added.

>
>>
>>   Submitted by:       jeff
>>   Reviewed by:        kib
>>
>> Modified:
>>   head/sys/kern/vfs_bio.c
>>
>> Modified: head/sys/kern/vfs_bio.c
>> ==============================================================================
>> --- head/sys/kern/vfs_bio.c   Wed Dec 16 00:09:57 2015        (r292298)
>> +++ head/sys/kern/vfs_bio.c   Wed Dec 16 00:13:16 2015        (r292299)
>> @@ -2909,7 +2909,7 @@ getnewbuf(struct vnode *vp, int slpflag,
>>       } while(buf_scan(false) == 0);
>>
>>       if (reserved)
>> -             bufspace_release(maxsize);
>> +             atomic_subtract_long(&bufspace, maxsize);
>>       if (bp != NULL) {
>>               bp->b_flags |= B_INVAL;
>>               brelse(bp);
>