search for: nr_tags

From: Kent Overstreet <kmo at daterainc.com> Percpu frontend for allocating ids. With percpu allocation (that works), it's impossible to guarantee it will always be possible to allocate all nr_tags - typically, some will be stuck on a remote percpu freelist where the current job can't get to them. We do guarantee that it will always be possible to allocate at least (nr_tags / 2) tags - this is done by keeping track of which and how many cpus have tags on their percpu freelists. On alloca...

..."Nicholas A. Bellinger" <nab at linux-iscsi.org> wrote: > From: Kent Overstreet <kmo at daterainc.com> > > Percpu frontend for allocating ids. With percpu allocation (that works), > it's impossible to guarantee it will always be possible to allocate all > nr_tags - typically, some will be stuck on a remote percpu freelist > where the current job can't get to them. > > We do guarantee that it will always be possible to allocate at least > (nr_tags / 2) tags - this is done by keeping track of which and how many > cpus have tags on their pe...

..."Nicholas A. Bellinger" <nab at linux-iscsi.org> wrote: > From: Kent Overstreet <kmo at daterainc.com> > > Percpu frontend for allocating ids. With percpu allocation (that works), > it's impossible to guarantee it will always be possible to allocate all > nr_tags - typically, some will be stuck on a remote percpu freelist > where the current job can't get to them. > > We do guarantee that it will always be possible to allocate at least > (nr_tags / 2) tags - this is done by keeping track of which and how many > cpus have tags on their pe...

From: Nicholas Bellinger <nab at linux-iscsi.org> Hi folks, This is an updated series for adding tag pre-allocation support of target fabric descriptor memory, utilizing Kent's latest per-cpu ida bits here, along with Christoph Lameter's latest comments: [PATCH 04/10] idr: Percpu ida http://marc.info/?l=linux-kernel&m=137160026006974&w=2 The first patch is a

From: Nicholas Bellinger <nab at linux-iscsi.org> Hi folks, This is an updated series for adding tag pre-allocation support of target fabric descriptor memory, utilizing Kent's latest per-cpu ida bits here, along with Christoph Lameter's latest comments: [PATCH 04/10] idr: Percpu ida http://marc.info/?l=linux-kernel&m=137160026006974&w=2 The first patch is a

...*pool, unsigned cpus_have_tags, cpu = pool->cpu_last_stolen; struct percpu_ida_cpu *remote; - for (cpus_have_tags = bitmap_weight(pool->cpus_have_tags, nr_cpu_ids); + for (cpus_have_tags = cpumask_weight(&pool->cpus_have_tags); cpus_have_tags * IDA_PCPU_SIZE > pool->nr_tags / 2; cpus_have_tags--) { - cpu = find_next_bit(pool->cpus_have_tags, nr_cpu_ids, cpu); + cpu = cpumask_next(cpu, &pool->cpus_have_tags); - if (cpu == nr_cpu_ids) - cpu = find_first_bit(pool->cpus_have_tags, nr_cpu_ids); + if (cpu >= nr_cpu_ids) + cpu = cpumask_first...

Removing the percpu_ida code nets over 400 lines of removal. It's not as spectacular as deleting an entire architecture, but it's still a worthy reduction in lines of code. Untested due to lack of hardware and not understanding how to set up a target platform. Changes from v1: - Fixed bugs pointed out by Jens in iscsit_wait_for_tag() - Abstracted out tag freeing as requested by Bart

Removing the percpu_ida code nets over 400 lines of removal. It's not as spectacular as deleting an entire architecture, but it's still a worthy reduction in lines of code. Untested due to lack of hardware and not understanding how to set up a target platform. Changes from v1: - Fixed bugs pointed out by Jens in iscsit_wait_for_tag() - Abstracted out tag freeing as requested by Bart

From: Matthew Wilcox <mawilcox at microsoft.com> This is a pretty rough-and-ready conversion of the target drivers from using percpu_ida to sbitmap. It compiles; I don't have a target setup, so it's completely untested. I haven't tried to do anything particularly clever here, so it's possible that, for example, the wait queue in iscsi_target_util could be more clever, like

...+ * Safe to be called from interrupt context. > > + */ > > +void percpu_ida_free(struct percpu_ida *pool, unsigned tag) > > +{ > > + struct percpu_ida_cpu *tags; > > + unsigned long flags; > > + unsigned nr_free; > > + > > + BUG_ON(tag >= pool->nr_tags); > > + > > + local_irq_save(flags); > > + tags = this_cpu_ptr(pool->tag_cpu); > > + > > + spin_lock(&tags->lock); > > Why do we need this lock, btw? It's a cpu-local structure and local > irqs are disabled... Tag stealing. I added a comment f...

...r avoid address calculation through segment prefixes. F.e. if (__this_cpu_read(tags->nrfree) { int n = __this_cpu_dec_return(tags->nr_free); tag = __this_cpu_read(tags->freelist[n]); } > + spin_unlock(&tags->lock); Drop. > + * Returns a tag - an integer in the range [0..nr_tags) (passed to > + * tag_pool_init()), or otherwise -ENOSPC on allocation failure. > + * > + * Safe to be called from interrupt context (assuming it isn't passed > + * __GFP_WAIT, of course). > + * > + * Will not fail if passed __GFP_WAIT. > + */ > +int percpu_ida_alloc(str...

...r avoid address calculation through segment prefixes. F.e. if (__this_cpu_read(tags->nrfree) { int n = __this_cpu_dec_return(tags->nr_free); tag = __this_cpu_read(tags->freelist[n]); } > + spin_unlock(&tags->lock); Drop. > + * Returns a tag - an integer in the range [0..nr_tags) (passed to > + * tag_pool_init()), or otherwise -ENOSPC on allocation failure. > + * > + * Safe to be called from interrupt context (assuming it isn't passed > + * __GFP_WAIT, of course). > + * > + * Will not fail if passed __GFP_WAIT. > + */ > +int percpu_ida_alloc(str...

...ce_show, }; diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index a54b4b070f1c..aafb44224c89 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -166,15 +166,15 @@ static struct attribute *default_ctx_attrs[] = { }; static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = { - .attr = {.name = "nr_tags", .mode = S_IRUGO }, + .attr = {.name = "nr_tags", .mode = 0444 }, .show = blk_mq_hw_sysfs_nr_tags_show, }; static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_reserved_tags = { - .attr = {.name = "nr_reserved_tags", .mode = S...

...ce_show, }; diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c index a54b4b070f1c..aafb44224c89 100644 --- a/block/blk-mq-sysfs.c +++ b/block/blk-mq-sysfs.c @@ -166,15 +166,15 @@ static struct attribute *default_ctx_attrs[] = { }; static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = { - .attr = {.name = "nr_tags", .mode = S_IRUGO }, + .attr = {.name = "nr_tags", .mode = 0444 }, .show = blk_mq_hw_sysfs_nr_tags_show, }; static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_reserved_tags = { - .attr = {.name = "nr_reserved_tags", .mode = S...