2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
2.12 /proc/<pid>/oom_adj - Adjust the oom-killer score
2.13 /proc/<pid>/oom_score - Display current oom-killer score
+ 2.14 /proc/<pid>/io - Display the IO accounting fields
------------------------------------------------------------------------------
Preface
this memory, making it slower to access than lowmem.
LowTotal:
LowFree: Lowmem is memory which can be used for everything that
- highmem can be used for, but it is also availble for the
+ highmem can be used for, but it is also available for the
kernel's use for its own data structures. Among many
other things, it is where everything from the Slab is
allocated. Bad things happen when you're out of lowmem.
you probably should increase the lower_zone_protection setting.
The units of this tunable are fairly vague. It is approximately equal
-to "megabytes". So setting lower_zone_protection=100 will protect around 100
+to "megabytes," so setting lower_zone_protection=100 will protect around 100
megabytes of the lowmem zone from user allocations. It will also make
-those 100 megabytes unavaliable for use by applications and by
+those 100 megabytes unavailable for use by applications and by
pagecache, so there is a cost.
The effects of this tunable may be observed by monitoring
address space are refused. Used for a typical system. It
ensures a seriously wild allocation fails while allowing
overcommit to reduce swap usage. root is allowed to
- allocate slighly more memory in this mode. This is the
+ allocate slightly more memory in this mode. This is the
default.
1 - Always overcommit. Appropriate for some scientific
be dropped. The default settings limit warning messages to one every five
seconds.
+warnings
+--------
+
+This controls console messages from the networking stack that can occur because
+of problems on the network like duplicate address or bad checksums. Normally,
+this should be enabled, but if the problem persists the messages can be
+disabled.
+
+
netdev_max_backlog
------------------
tcp_ecn
-------
-This file controls the use of the ECN bit in the IPv4 headers, this is a new
+This file controls the use of the ECN bit in the IPv4 headers. This is a new
feature about Explicit Congestion Notification, but some routers and firewalls
-block trafic that has this bit set, so it could be necessary to echo 0 to
-/proc/sys/net/ipv4/tcp_ecn, if you want to talk to this sites. For more info
+block traffic that has this bit set, so it could be necessary to echo 0 to
+/proc/sys/net/ipv4/tcp_ecn if you want to talk to these sites. For more info
you could read RFC2481.
tcp_retrans_collapse
default is to use the BSD compatible interpretation of the urgent pointer
pointing to the first byte after the urgent data. The RFC793 interpretation is
to have it point to the last byte of urgent data. Enabling this option may
-lead to interoperatibility problems. Disabled by default.
+lead to interoperability problems. Disabled by default.
tcp_syncookies
--------------
These parameters are used to limit how many ICMP destination unreachable to
send from the host in question. ICMP destination unreachable messages are
-sent when we can not reach the next hop, while trying to transmit a packet.
+sent when we cannot reach the next hop while trying to transmit a packet.
It will also print some error messages to kernel logs if someone is ignoring
our ICMP redirects. The higher the error_cost factor is, the fewer
destination unreachable and error messages will be let through. Error_burst
Maximum queue length of the delayed proxy arp timer. (see proxy_delay).
-app_solcit
+app_solicit
----------
Determines the number of requests to send to the user level ARP daemon. Use 0
command to write value into these files, thereby changing the default settings
of the kernel.
------------------------------------------------------------------------------
+
+2.14 /proc/<pid>/io - Display the IO accounting fields
+-------------------------------------------------------
+
+This file contains IO statistics for each running process
+
+Example
+-------
+
+test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
+[1] 3828
+
+test:/tmp # cat /proc/3828/io
+rchar: 323934931
+wchar: 323929600
+syscr: 632687
+syscw: 632675
+read_bytes: 0
+write_bytes: 323932160
+cancelled_write_bytes: 0
+
+
+Description
+-----------
+
+rchar
+-----
+
+I/O counter: chars read
+The number of bytes which this task has caused to be read from storage. This
+is simply the sum of bytes which this process passed to read() and pread().
+It includes things like tty IO and it is unaffected by whether or not actual
+physical disk IO was required (the read might have been satisfied from
+pagecache)
+
+
+wchar
+-----
+
+I/O counter: chars written
+The number of bytes which this task has caused, or shall cause to be written
+to disk. Similar caveats apply here as with rchar.
+
+
+syscr
+-----
+
+I/O counter: read syscalls
+Attempt to count the number of read I/O operations, i.e. syscalls like read()
+and pread().
+
+
+syscw
+-----
+
+I/O counter: write syscalls
+Attempt to count the number of write I/O operations, i.e. syscalls like
+write() and pwrite().
+
+
+read_bytes
+----------
+
+I/O counter: bytes read
+Attempt to count the number of bytes which this process really did cause to
+be fetched from the storage layer. Done at the submit_bio() level, so it is
+accurate for block-backed filesystems. <please add status regarding NFS and
+CIFS at a later time>
+
+
+write_bytes
+-----------
+
+I/O counter: bytes written
+Attempt to count the number of bytes which this process caused to be sent to
+the storage layer. This is done at page-dirtying time.
+
+
+cancelled_write_bytes
+---------------------
+
+The big inaccuracy here is truncate. If a process writes 1MB to a file and
+then deletes the file, it will in fact perform no writeout. But it will have
+been accounted as having caused 1MB of write.
+In other words: The number of bytes which this process caused to not happen,
+by truncating pagecache. A task can cause "negative" IO too. If this task
+truncates some dirty pagecache, some IO which another task has been accounted
+for (in it's write_bytes) will not be happening. We _could_ just subtract that
+from the truncating task's write_bytes, but there is information loss in doing
+that.
+
+
+Note
+----
+
+At its current implementation state, this is a bit racy on 32-bit machines: if
+process A reads process B's /proc/pid/io while process B is updating one of
+those 64-bit counters, process A could see an intermediate result.
+
+
+More information about this can be found within the taskstats documentation in
+Documentation/accounting.
+
+------------------------------------------------------------------------------
git.samba.org / sfrench / cifs-2.6.git / blobdiff