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Groups > linux.kernel > #1174129 > unrolled thread
| Started by | Dave Chinner <david@fromorbit.com> |
|---|---|
| First post | 2015-06-29 23:50 +0200 |
| Last post | 2015-07-02 02:30 +0200 |
| Articles | 3 — 2 participants |
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Re: [PATCH] XFS: Delete unnecessary checks before the function call "xfs_qm_dqrele" Dave Chinner <david@fromorbit.com> - 2015-06-29 23:50 +0200
Re: XFS: Fine-tuning for checks before the function call "xfs_qm_dqrele"? SF Markus Elfring <elfring@users.sourceforge.net> - 2015-07-01 10:00 +0200
Re: XFS: Fine-tuning for checks before the function call "xfs_qm_dqrele"? Dave Chinner <david@fromorbit.com> - 2015-07-02 02:30 +0200
| From | Dave Chinner <david@fromorbit.com> |
|---|---|
| Date | 2015-06-29 23:50 +0200 |
| Subject | Re: [PATCH] XFS: Delete unnecessary checks before the function call "xfs_qm_dqrele" |
| Message-ID | <pGP6d-79Z-103@gated-at.bofh.it> |
On Fri, Jun 26, 2015 at 11:15:31AM +0200, SF Markus Elfring wrote: > From: Markus Elfring <elfring@users.sourceforge.net> > Date: Fri, 26 Jun 2015 11:05:41 +0200 > > The xfs_qm_dqrele() function tests whether its argument is NULL and > then returns immediately. True. > Thus the test around the call is not needed. But wrong. xfs_dqrele_inode() gets called on every inode in the inode cache, and this change results in a cacheline in every inode being dirtied even if they don't have dquots attached. Given the inode cache can hold tens to hundreds of millions of inodes on large machines, we don't want to dirty any cachelines we don't need to while walking the inode cache and releasing dquots... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | SF Markus Elfring <elfring@users.sourceforge.net> |
|---|---|
| Date | 2015-07-01 10:00 +0200 |
| Subject | Re: XFS: Fine-tuning for checks before the function call "xfs_qm_dqrele"? |
| Message-ID | <pHl63-2i0-37@gated-at.bofh.it> |
| In reply to | #1174129 |
> xfs_dqrele_inode() gets called on every inode in the inode cache, > and this change results in a cacheline in every inode being dirtied > even if they don't have dquots attached. Given the inode cache can > hold tens to hundreds of millions of inodes on large machines, we > don't want to dirty any cachelines we don't need to while walking > the inode cache and releasing dquots... Would it make sense to annotate checks before such function calls as "LIKELY"? Regards, Markus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Dave Chinner <david@fromorbit.com> |
|---|---|
| Date | 2015-07-02 02:30 +0200 |
| Subject | Re: XFS: Fine-tuning for checks before the function call "xfs_qm_dqrele"? |
| Message-ID | <pHAy5-3RE-5@gated-at.bofh.it> |
| In reply to | #1175060 |
On Wed, Jul 01, 2015 at 09:50:00AM +0200, SF Markus Elfring wrote: > > xfs_dqrele_inode() gets called on every inode in the inode cache, > > and this change results in a cacheline in every inode being dirtied > > even if they don't have dquots attached. Given the inode cache can > > hold tens to hundreds of millions of inodes on large machines, we > > don't want to dirty any cachelines we don't need to while walking > > the inode cache and releasing dquots... > > Would it make sense to annotate checks before such function calls > as "LIKELY"? No - it will be random as to whether the inodes have dquots attached or not and so a static hint is always going to be wrong for someone.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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