- 06 Jan, 2009 1 commit
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Eric Dumazet authored
For NR_CPUS >= 16 values, FBC_BATCH is 2*NR_CPUS Considering more and more distros are using high NR_CPUS values, it makes sense to use a more sensible value for FBC_BATCH, and get rid of NR_CPUS. A sensible value is 2*num_online_cpus(), with a minimum value of 32 (This minimum value helps branch prediction in __percpu_counter_add()) We already have a hotcpu notifier, so we can adjust FBC_BATCH dynamically. We rename FBC_BATCH to percpu_counter_batch since its not a constant anymore. Signed-off-by:
Eric Dumazet <dada1@cosmosbay.com> Acked-by:
David S. Miller <davem@davemloft.net> Acked-by:
Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- 29 Dec, 2008 1 commit
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Peter Zijlstra authored
Impact: fix lockdep false positives Classify percpu_counter instances similar to regular lock objects -- that is, per instantiation site. The networking code has increased its use of percpu_counters, which leads to false positives if they are treated as a single class. Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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- 10 Dec, 2008 3 commits
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Andrew Morton authored
Revert commit e8ced39d Author: Mingming Cao <cmm@us.ibm.com> Date: Fri Jul 11 19:27:31 2008 -0400 percpu_counter: new function percpu_counter_sum_and_set As described in revert "percpu counter: clean up percpu_counter_sum_and_set()" the new percpu_counter_sum_and_set() is racy against updates to the cpu-local accumulators on other CPUs. Revert that change. This means that ext4 will be slow again. But correct. Reported-by: -
Andrew Morton authored
Revert commit 1f7c14c6 Author: Mingming Cao <cmm@us.ibm.com> Date: Thu Oct 9 12:50:59 2008 -0400 percpu counter: clean up percpu_counter_sum_and_set() Before this patch we had the following: percpu_counter_sum(): return the percpu_counter's value percpu_counter_sum_and_set(): return the percpu_counter's value, copying that value into the central value and zeroing the per-cpu counters before returning. After this patch, percpu_counter_sum_and_set() has gone, and percpu_counter_sum() gets the old percpu_counter_sum_and_set() functionality. Problem is, as Eric points out, the old percpu_counter_sum_and_set() functionality was racy and wrong. It zeroes out counters on "other" cpus, without holding any locks which will prevent races agaist updates from those other CPUS. This patch reverts 1f7c14c6. This means that percpu_counter_sum_and_set() still has the race, but percpu_counter_sum() does not. Note that this is not a simple revert - ext4 has since started using percpu_counter_sum() for its dirty_blocks counter as well. Note that this revert patch changes percpu_counter_sum() semantics. Before the patch, a call to percpu_counter_sum() will bring the counter's central counter mostly up-to-date, so a following percpu_counter_read() will return a close value. After this patch, a call to percpu_counter_sum() will leave the counter's central accumulator unaltered, so a subsequent call to percpu_counter_read() can now return a significantly inaccurate result. If there is any code in the tree which was introduced after e8ced39d was merged, and which depends upon the new percpu_counter_sum() semantics, that code will break. Reported-by: -
Eric Dumazet authored
We should first delete the counter from percpu_counters list before freeing memory, or a percpu_counter_hotcpu_callback() could dereference a NULL pointer. Signed-off-by:
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- 09 Oct, 2008 1 commit
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Mingming Cao authored
percpu_counter_sum_and_set() and percpu_counter_sum() is the same except the former updates the global counter after accounting. Since we are taking the fbc->lock to calculate the precise value of the counter in percpu_counter_sum() anyway, it should simply set fbc->count too, as the percpu_counter_sum_and_set() does. This patch merges these two interfaces into one. Signed-off-by:
Mingming Cao <cmm@us.ibm.com> Acked-by:
"Theodore Ts'o" <tytso@mit.edu>
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- 11 Jul, 2008 1 commit
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Mingming Cao authored
Delayed allocation need to check free blocks at every write time. percpu_counter_read_positive() is not quit accurate. delayed allocation need a more accurate accounting, but using percpu_counter_sum_positive() is frequently is quite expensive. This patch added a new function to update center counter when sum per-cpu counter, to increase the accurate rate for next percpu_counter_read() and require less calling expensive percpu_counter_sum(). Signed-off-by:
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- 30 Apr, 2008 1 commit
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Peter Zijlstra authored
Provide a place in sysfs (/sys/class/bdi) for the backing_dev_info object. This allows us to see and set the various BDI specific variables. In particular this properly exposes the read-ahead window for all relevant users and /sys/block/<block>/queue/read_ahead_kb should be deprecated. With patient help from Kay Sievers and Greg KH [mszeredi@suse.cz] - split off NFS and FUSE changes into separate patches - document new sysfs attributes under Documentation/ABI - do bdi_class_init as a core_initcall, otherwise the "default" BDI won't be initialized - remove bdi_init_fmt macro, it's not used very much [akpm@linux-foundation.org: fix ia64 warning] Signed-off-by:
Greg KH <greg@kroah.com> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Signed-off-by:
Miklos Szeredi <mszeredi@suse.cz> Signed-off-by:
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- 19 Oct, 2007 1 commit
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Gautham R Shenoy authored
Some of the per-cpu counters and thus their locks are accessed from IRQ contexts. This can cause a deadlock if it interrupts a cpu-offline thread which is transferring a dead-cpu's counts to the global counter. Add appropriate IRQ protection in the cpu-hotplug callback path. Signed-off-by:
Gautham R Shenoy <ego@in.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:
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- 17 Oct, 2007 8 commits
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Peter Zijlstra authored
provide a way to tell lockdep about percpu_counters that are supposed to be used from irq safe contexts. Signed-off-by:
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Peter Zijlstra authored
alloc_percpu can fail, propagate that error. Signed-off-by:
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Peter Zijlstra authored
Provide an accurate version of percpu_counter_read. Signed-off-by:
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Peter Zijlstra authored
s/percpu_counter_sum/&_positive/ Because its consitent with percpu_counter_read* Signed-off-by:
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Peter Zijlstra authored
Provide a method to set a percpu counter to a specified value. Signed-off-by:
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Peter Zijlstra authored
percpu_counter is a s64 counter, make _add consitent. Signed-off-by:
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Peter Zijlstra authored
Because the current batch setup has an quadric error bound on the counter, allow for an alternative setup. Signed-off-by:
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Peter Zijlstra authored
s/percpu_counter_mod/percpu_counter_add/ Because its a better name, _mod implies modulo. Signed-off-by:
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- 16 Jul, 2007 2 commits
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Andrew Morton authored
Now that we have implemented hotunplug-time counter spilling, percpu_counter_sum() only needs to look at online CPUs. Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
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Andrew Morton authored
per-cpu counters presently must iterate over all possible CPUs in the exhaustive percpu_counter_sum(). But it can be much better to only iterate over the presently-online CPUs. To do this, we must arrange for an offlined CPU's count to be spilled into the counter's central count. We can do this for all percpu_counters in the machine by linking them into a single global list and walking that list at CPU_DEAD time. (I hope. Might have race windows in which the percpu_counter_sum() count is inaccurate?) Cc: Gautham R Shenoy <ego@in.ibm.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:
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- 23 Jun, 2006 2 commits
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Mingming Cao authored
The percpu counter data type are changed in this set of patches to support more users like ext3 who need more than 32 bit to store the free blocks total in the filesystem. - Generic perpcu counters data type changes. The size of the global counter and local counter were explictly specified using s64 and s32. The global counter is changed from long to s64, while the local counter is changed from long to s32, so we could avoid doing 64 bit update in most cases. - Users of the percpu counters are updated to make use of the new percpu_counter_init() routine now taking an additional parameter to allow users to pass the initial value of the global counter. Signed-off-by:
Andrew Morton <akpm@osdl.org> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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Ravikiran G Thirumalai authored
- Move percpu_counter routines from mm/swap.c to lib/percpu_counter.c Signed-off-by:
Ravikiran Thirumalai <kiran@scalex86.org> Signed-off-by:
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