| Message ID | 20201015142416.70294-3-roger.pau@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/blkback: add LRU purge parameters | expand |
On 15.10.20 16:24, Roger Pau Monne wrote: > Assume that reads and writes to the variable will be atomic. The worse > that could happen is that one of the purges removes a partially > written percentage of grants, but the cache itself will recover. > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > --- > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Cc: Jens Axboe <axboe@kernel.dk> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> > Cc: SeongJae Park <sjpark@amazon.de> > Cc: xen-devel@lists.xenproject.org > Cc: linux-block@vger.kernel.org > Cc: J. Roeleveld <joost@antarean.org> > Cc: Jürgen Groß <jgross@suse.com> > --- > Documentation/ABI/testing/sysfs-driver-xen-blkback | 9 +++++++++ > drivers/block/xen-blkback/blkback.c | 7 +++++-- > 2 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback > index 776f25d335ca..7de791ad61f9 100644 > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback > @@ -45,3 +45,12 @@ Description: > to be executed periodically. This parameter controls the time > interval between consecutive executions of the purge mechanism > is set in ms. > + > +What: /sys/module/xen_blkback/parameters/lru_percent_clean > +Date: October 2020 > +KernelVersion: 5.10 > +Contact: Roger Pau Monné <roger.pau@citrix.com> > +Description: > + When the persistent grants list is full we will remove unused > + grants from the list. The percent number of grants to be > + removed at each LRU execution. > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c > index 6ad9b76fdb2b..772852d45a5a 100644 > --- a/drivers/block/xen-blkback/blkback.c > +++ b/drivers/block/xen-blkback/blkback.c > @@ -127,7 +127,10 @@ MODULE_PARM_DESC(lru_internval, > * from the list. The percent number of grants to be removed at each LRU > * execution. > */ > -#define LRU_PERCENT_CLEAN 5 > +static unsigned int lru_percent_clean = 5; > +module_param_named(lru_percent_clean, lru_percent_clean, uint, 0644); > +MODULE_PARM_DESC(lru_percent_clean, > + "Percentage of persistent grants to remove from the cache when full"); > > /* Run-time switchable: /sys/module/blkback/parameters/ */ > static unsigned int log_stats; > @@ -404,7 +407,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) > !ring->blkif->vbd.overflow_max_grants)) { > num_clean = 0; > } else { > - num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN; > + num_clean = (max_pgrants / 100) * lru_percent_clean; Hmm, wouldn't it be better to use (max_grants * lru_percent_clean) / 100 here in order to support max_grants values less than 100? Juergen
On Thu, Oct 15, 2020 at 04:37:52PM +0200, Jürgen Groß wrote: > On 15.10.20 16:24, Roger Pau Monne wrote: > > Assume that reads and writes to the variable will be atomic. The worse > > that could happen is that one of the purges removes a partially > > written percentage of grants, but the cache itself will recover. > > > > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> > > --- > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > > Cc: Jens Axboe <axboe@kernel.dk> > > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> > > Cc: SeongJae Park <sjpark@amazon.de> > > Cc: xen-devel@lists.xenproject.org > > Cc: linux-block@vger.kernel.org > > Cc: J. Roeleveld <joost@antarean.org> > > Cc: Jürgen Groß <jgross@suse.com> > > --- > > Documentation/ABI/testing/sysfs-driver-xen-blkback | 9 +++++++++ > > drivers/block/xen-blkback/blkback.c | 7 +++++-- > > 2 files changed, 14 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback > > index 776f25d335ca..7de791ad61f9 100644 > > --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback > > +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback > > @@ -45,3 +45,12 @@ Description: > > to be executed periodically. This parameter controls the time > > interval between consecutive executions of the purge mechanism > > is set in ms. > > + > > +What: /sys/module/xen_blkback/parameters/lru_percent_clean > > +Date: October 2020 > > +KernelVersion: 5.10 > > +Contact: Roger Pau Monné <roger.pau@citrix.com> > > +Description: > > + When the persistent grants list is full we will remove unused > > + grants from the list. The percent number of grants to be > > + removed at each LRU execution. > > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c > > index 6ad9b76fdb2b..772852d45a5a 100644 > > --- a/drivers/block/xen-blkback/blkback.c > > +++ b/drivers/block/xen-blkback/blkback.c > > @@ -127,7 +127,10 @@ MODULE_PARM_DESC(lru_internval, > > * from the list. The percent number of grants to be removed at each LRU > > * execution. > > */ > > -#define LRU_PERCENT_CLEAN 5 > > +static unsigned int lru_percent_clean = 5; > > +module_param_named(lru_percent_clean, lru_percent_clean, uint, 0644); > > +MODULE_PARM_DESC(lru_percent_clean, > > + "Percentage of persistent grants to remove from the cache when full"); > > /* Run-time switchable: /sys/module/blkback/parameters/ */ > > static unsigned int log_stats; > > @@ -404,7 +407,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) > > !ring->blkif->vbd.overflow_max_grants)) { > > num_clean = 0; > > } else { > > - num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN; > > + num_clean = (max_pgrants / 100) * lru_percent_clean; > > Hmm, wouldn't it be better to use (max_grants * lru_percent_clean) / 100 > here in order to support max_grants values less than 100? Yes, we should have done that when moving max_pgrants to a parameter, it used to be fixed first. Will do in next version since I'm already changing the line. Thanks, Roger.
diff --git a/Documentation/ABI/testing/sysfs-driver-xen-blkback b/Documentation/ABI/testing/sysfs-driver-xen-blkback index 776f25d335ca..7de791ad61f9 100644 --- a/Documentation/ABI/testing/sysfs-driver-xen-blkback +++ b/Documentation/ABI/testing/sysfs-driver-xen-blkback @@ -45,3 +45,12 @@ Description: to be executed periodically. This parameter controls the time interval between consecutive executions of the purge mechanism is set in ms. + +What: /sys/module/xen_blkback/parameters/lru_percent_clean +Date: October 2020 +KernelVersion: 5.10 +Contact: Roger Pau Monné <roger.pau@citrix.com> +Description: + When the persistent grants list is full we will remove unused + grants from the list. The percent number of grants to be + removed at each LRU execution. diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c index 6ad9b76fdb2b..772852d45a5a 100644 --- a/drivers/block/xen-blkback/blkback.c +++ b/drivers/block/xen-blkback/blkback.c @@ -127,7 +127,10 @@ MODULE_PARM_DESC(lru_internval, * from the list. The percent number of grants to be removed at each LRU * execution. */ -#define LRU_PERCENT_CLEAN 5 +static unsigned int lru_percent_clean = 5; +module_param_named(lru_percent_clean, lru_percent_clean, uint, 0644); +MODULE_PARM_DESC(lru_percent_clean, + "Percentage of persistent grants to remove from the cache when full"); /* Run-time switchable: /sys/module/blkback/parameters/ */ static unsigned int log_stats; @@ -404,7 +407,7 @@ static void purge_persistent_gnt(struct xen_blkif_ring *ring) !ring->blkif->vbd.overflow_max_grants)) { num_clean = 0; } else { - num_clean = (max_pgrants / 100) * LRU_PERCENT_CLEAN; + num_clean = (max_pgrants / 100) * lru_percent_clean; num_clean = ring->persistent_gnt_c - max_pgrants + num_clean; num_clean = min(ring->persistent_gnt_c, num_clean); pr_debug("Going to purge at least %u persistent grants\n",
Assume that reads and writes to the variable will be atomic. The worse that could happen is that one of the purges removes a partially written percentage of grants, but the cache itself will recover. Signed-off-by: Roger Pau Monné <roger.pau@citrix.com> --- Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: SeongJae Park <sjpark@amazon.de> Cc: xen-devel@lists.xenproject.org Cc: linux-block@vger.kernel.org Cc: J. Roeleveld <joost@antarean.org> Cc: Jürgen Groß <jgross@suse.com> --- Documentation/ABI/testing/sysfs-driver-xen-blkback | 9 +++++++++ drivers/block/xen-blkback/blkback.c | 7 +++++-- 2 files changed, 14 insertions(+), 2 deletions(-)