How sync_file_range() really works
There is a relatively new and platform dependent flushing function called sync_file_range(). Some databases (not MySQL) use sync_file_range() internally. Recently I investigated stall issues caused by buffered write and sync_file_range(). I learned a lot during investigation but I don't think these behaviors are well known to the public. Here I summarize my understandings. Understanding difference
Tracing and Profiling - Yocto Project
Tracing and Profiling in Yocto Yocto bundles a number of tracing and profiling tools - this 'HOWTO' describes their basic usage and shows by example how to make use of them to examine application and system behavior. The tools presented are for the most part completely open-ended and have quite good and/or extensive documentation of their own which can be used to solve just about any problem you m
iostat: (r/s + w/s) * svctm = %util on Linux
iostat -x is very useful to check disk i/o activities. Sometimes it is said that "check %util is less than 100%" or "check svctm is less than 50ms", but please do not fully trust these numbers. For example, the following two cases (DBT-2 load on MySQL) used same disks (two HDD disks, RAID1) and reached almost 100% util, but performance numbers were very different (no.2 was about twice as fast as n
iostat ã®è¦‹æ–¹ - ablog
出力例 $ iostat -x 30 avg-cpu: %user %nice %system %iowait %steal %idle 0.87 0.01 2.53 0.49 0.00 96.11 Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.05 16.03 0.36 13.74 5.77 238.22 17.31 0.15 10.39 0.98 1.38 sda1 0.00 0.00 0.00 0.00 0.00 0.00 15.53 0.00 12.81 11.47 0.00 sda2 0.05 16.03 0.36 13.74 5.77 238.22 17.31 0.15 10.39 0.98 1.38 avg-cpu: %user %nice %syst
iostat await svctm 㮠見ã‹ãŸã€è€ƒãˆæ–¹
4. 4  下記ã¯iostat -x ã®ãƒã‚°ã®ã‚µãƒ³ãƒ—ル iostat -x 1 ： avg-cpu: %user %nice %system %iowait %steal %idle 0.76 0.00 0.51 1.52 0.00 97.22 Device: rrqm/s … rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util sda 0.00 … 2000.00 88.00 208.80 0.14 13.70 8.00 8.00 sdb 0.00 … 0.00 24.00 8.00 0.09 31.33 21.67 6.50 avg-cpu: %user %nice %system %iowait %steal %idle 0.76 0.00 0.51 0.25 0.00 98.48 Device: rrqm/s … rsec/s ws
Fsync Performance on Storage Devices
All of Percona’s open-source software products, in one place, to download as much or as little as you need.
ScyllaDB’s Compaction Strategies Series: Space Amplification in Size-Tiered Compaction
This is the first post in a series of four about the different compaction strategies available in ScyllaDB. The series will look at the good and the bad properties of each compaction strategy, and how to choose the best compaction strategy for your workload. This first post will focus on ScyllaDB’s default compaction strategy, size-tiered compaction strategy. Although we’ll discuss the ScyllaDB da
Efficient File Copying On Linux
In response to my last post about dd, a friend of mine noticed that GNU cp always uses a 128 KB buffer size when copying a regular file; this is also the buffer size used by GNU cat. If you use strace to watch what happens when copying a file, you should see a lot of 128 KB read/write sequences: $ strace -s 8 -xx cp /dev/urandom /dev/null ... read(3, "\x61\xca\xf8\xff\x1a\xd6\x83\x8b"..., 131072)
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How I Use iostat and vmstat for Performance Analysis - Yubin Xia
Better Linux Disk Caching & Performance with vm.dirty_ratio
databasss – Medium
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