Re: what's cooking in zram for 4.1
On (05/18/15 22:55), Minchan Kim wrote: > > > Why do you need all in one file? ... to provide consistent statistics? > > > > > > > yes, that's the main reason. > > In my side, other main reason was to reduce the number of system call > to see statistics. It is not only syscall overhead itself but also > causes slightly high-order allocation for kernel internal data structure > via slab allocation which is bad on low memory situation where is > frequent in zram-swap. Slab allocation could be fallback with 0-order > pages but it could cause excessive page reclaim seriously since compaction > didn't work. > Yes, it's a one of problem of current VM but there is no reason to hesitate > if we can avoid such problems and support consistent statistic as well. > true. syscalls and corresponding error handling for each one of them were on a list: https://www.marc.info/?l=linux-kernel&m=142586445420298&w=2 Karel has a remarkably good codebase, so error handling would not be an issue :-) that's why consistent stats moved forward. in general, increasing consistency and reducing the syscall pressure are good enough to move on. -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
On Mon, May 18, 2015 at 06:56:49PM +0900, Sergey Senozhatsky wrote: > On (05/18/15 11:36), Karel Zak wrote: > > On Sat, May 09, 2015 at 01:21:48PM +0900, Sergey Senozhatsky wrote: > > > There will be some user-space visible changes in zram 4.1 we'd love to > > > let you know > > > about. > > > > ... > > > > > -- /sys/block/zram/mm_stat > > > > > > The stat file represents device's mm statistics. It consists of a single > > > line of text and contains the following stats separated by whitespace: > > > orig_data_size > > > compr_data_size > > > mem_used_total > > > mem_limit > > > mem_used_max > > > zero_pages > > > num_migrated > > > > OK, zramctl(8) code in util-linux git tree supports mm_stat file now. > > It's able to fallback to the original /sys/block/zram/ if > > mm_stat does not exist. The change will be available in v2.27 (~Aug 2015). > > > > I have also added support for MEM-LIMIT, MEM-USED and MIGRATED columns. > > > > great, thanks! Thanks, guys! -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
Hello On Mon, May 11, 2015 at 08:56:02PM +0900, Sergey Senozhatsky wrote: > On (05/11/15 13:38), Karel Zak wrote: > > hmm... frankly, the reason why I love /sys and why hate /proc is > > value-per-file. You do not need special parsers to read from /sys > > (usually). > > > > > orig_data_size > > > compr_data_size > > > mem_used_total > > > mem_limit > > > mem_used_max > > > zero_pages > > > num_migrated > > > > Why do you need all in one file? ... to provide consistent statistics? > > > > yes, that's the main reason. In my side, other main reason was to reduce the number of system call to see statistics. It is not only syscall overhead itself but also causes slightly high-order allocation for kernel internal data structure via slab allocation which is bad on low memory situation where is frequent in zram-swap. Slab allocation could be fallback with 0-order pages but it could cause excessive page reclaim seriously since compaction didn't work. Yes, it's a one of problem of current VM but there is no reason to hesitate if we can avoid such problems and support consistent statistic as well. -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
On (05/18/15 11:36), Karel Zak wrote: > On Sat, May 09, 2015 at 01:21:48PM +0900, Sergey Senozhatsky wrote: > > There will be some user-space visible changes in zram 4.1 we'd love to let > > you know > > about. > > ... > > > -- /sys/block/zram/mm_stat > > > > The stat file represents device's mm statistics. It consists of a single > > line of text and contains the following stats separated by whitespace: > > orig_data_size > > compr_data_size > > mem_used_total > > mem_limit > > mem_used_max > > zero_pages > > num_migrated > > OK, zramctl(8) code in util-linux git tree supports mm_stat file now. > It's able to fallback to the original /sys/block/zram/ if > mm_stat does not exist. The change will be available in v2.27 (~Aug 2015). > > I have also added support for MEM-LIMIT, MEM-USED and MIGRATED columns. > great, thanks! -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
On Sat, May 09, 2015 at 01:21:48PM +0900, Sergey Senozhatsky wrote: > There will be some user-space visible changes in zram 4.1 we'd love to let > you know > about. ... > -- /sys/block/zram/mm_stat > > The stat file represents device's mm statistics. It consists of a single > line of text and contains the following stats separated by whitespace: > orig_data_size > compr_data_size > mem_used_total > mem_limit > mem_used_max > zero_pages > num_migrated OK, zramctl(8) code in util-linux git tree supports mm_stat file now. It's able to fallback to the original /sys/block/zram/ if mm_stat does not exist. The change will be available in v2.27 (~Aug 2015). I have also added support for MEM-LIMIT, MEM-USED and MIGRATED columns. Karel -- Karel Zak http://karelzak.blogspot.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
On (05/11/15 13:38), Karel Zak wrote: > hmm... frankly, the reason why I love /sys and why hate /proc is > value-per-file. You do not need special parsers to read from /sys > (usually). > > > orig_data_size > > compr_data_size > > mem_used_total > > mem_limit > > mem_used_max > > zero_pages > > num_migrated > > Why do you need all in one file? ... to provide consistent statistics? > yes, that's the main reason. -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: what's cooking in zram for 4.1
On Sat, May 09, 2015 at 01:21:48PM +0900, Sergey Senozhatsky wrote: > There will be some user-space visible changes in zram 4.1 we'd love to let > you know > about. Thanks. > 2) zram has deprecated some of the existing stat sysfs attributes. we will > consolidate zramX device's stats in 3 files, rather than having N files > (per-stat). sysfs attributes used by zramctl(8) are: disksize orig_data_size compr_data_size comp_algorithm max_comp_streams mem_used_total reset > -- /sys/block/zram/mm_stat > > The stat file represents device's mm statistics. It consists of a single > line of text and contains the following stats separated by whitespace: hmm... frankly, the reason why I love /sys and why hate /proc is value-per-file. You do not need special parsers to read from /sys (usually). > orig_data_size > compr_data_size > mem_used_total > mem_limit > mem_used_max > zero_pages > num_migrated Why do you need all in one file? ... to provide consistent statistics? Karel -- Karel Zak http://karelzak.blogspot.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
what's cooking in zram for 4.1
Hello Karel, There will be some user-space visible changes in zram 4.1 we'd love to let you know about. 1) new sysfs node -- /sys/block/zramX/compact triggers zram memory compaction. 2) zram has deprecated some of the existing stat sysfs attributes. we will consolidate zramX device's stats in 3 files, rather than having N files (per-stat). The idea is: -- the existing RW sysfs device nodes will be downgraded to WO nodes (in linux 4.11) -- deprecated RO sysfs nodes will eventually be removed (in linux 4.11) User-space is advised to use the following files: -- /sys/block/zram/stat Represents block layer statistics (read Documentation/block/stat.txt for details). -- /sys/block/zram/io_stat The stat file represents device's I/O statistics not accounted by block layer and, thus, not available in zram/stat file. It consists of a single line of text and contains the following stats separated by whitespace: failed_reads failed_writes invalid_io notify_free -- /sys/block/zram/mm_stat The stat file represents device's mm statistics. It consists of a single line of text and contains the following stats separated by whitespace: orig_data_size compr_data_size mem_used_total mem_limit mem_used_max zero_pages num_migrated deprecated nodes will be around up until linux 4.11 (approx 2 years from now). in the meantime, zram will warn (once) should any user space app access any of the deprecated attrs: "zram: 30788 (cat) Attribute num_reads (and others) will be removed. See zram documentation." -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
