16c00db4bb
Pull AFS fixes from David Howells:
"Here's a set of patches that fix a number of bugs in the in-kernel AFS
client, including:
- Fix directory locking to not use individual page locks for
directory reading/scanning but rather to use a semaphore on the
afs_vnode struct as the directory contents must be read in a single
blob and data from different reads must not be mixed as the entire
contents may be shuffled about between reads.
- Fix address list parsing to handle port specifiers correctly.
- Only give up callback records on a server if we actually talked to
that server (we might not be able to access a server).
- Fix some callback handling bugs, including refcounting,
whole-volume callbacks and when callbacks actually get broken in
response to a CB.CallBack op.
- Fix some server/address rotation bugs, including giving up if we
can't probe a server; giving up if a server says it doesn't have a
volume, but there are more servers to try.
- Fix the decoding of fetched statuses to be OpenAFS compatible.
- Fix the handling of server lookups in Cache Manager ops (such as
CB.InitCallBackState3) to use a UUID if possible and to handle no
server being found.
- Fix a bug in server lookup where not all addresses are compared.
- Fix the non-encryption of calls that prevents some servers from
being accessed (this also requires an AF_RXRPC patch that has
already gone in through the net tree).
There's also a patch that adds tracepoints to log Cache Manager ops
that don't find a matching server, either by UUID or by address"
* tag 'afs-fixes-20180514' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
afs: Fix the non-encryption of calls
afs: Fix CB.CallBack handling
afs: Fix whole-volume callback handling
afs: Fix afs_find_server search loop
afs: Fix the handling of an unfound server in CM operations
afs: Add a tracepoint to record callbacks from unlisted servers
afs: Fix the handling of CB.InitCallBackState3 to find the server by UUID
afs: Fix VNOVOL handling in address rotation
afs: Fix AFSFetchStatus decoder to provide OpenAFS compatibility
afs: Fix server rotation's handling of fileserver probe failure
afs: Fix refcounting in callback registration
afs: Fix giving up callbacks on server destruction
afs: Fix address list parsing
afs: Fix directory page locking
109 lines
3.3 KiB
Plaintext
109 lines
3.3 KiB
Plaintext
Overhead calculation
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--------------------
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The overhead can be shown in two columns as 'Children' and 'Self' when
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perf collects callchains. The 'self' overhead is simply calculated by
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adding all period values of the entry - usually a function (symbol).
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This is the value that perf shows traditionally and sum of all the
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'self' overhead values should be 100%.
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The 'children' overhead is calculated by adding all period values of
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the child functions so that it can show the total overhead of the
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higher level functions even if they don't directly execute much.
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'Children' here means functions that are called from another (parent)
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function.
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It might be confusing that the sum of all the 'children' overhead
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values exceeds 100% since each of them is already an accumulation of
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'self' overhead of its child functions. But with this enabled, users
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can find which function has the most overhead even if samples are
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spread over the children.
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Consider the following example; there are three functions like below.
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-----------------------
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void foo(void) {
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/* do something */
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}
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void bar(void) {
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/* do something */
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foo();
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}
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int main(void) {
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bar()
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return 0;
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}
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-----------------------
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In this case 'foo' is a child of 'bar', and 'bar' is an immediate
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child of 'main' so 'foo' also is a child of 'main'. In other words,
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'main' is a parent of 'foo' and 'bar', and 'bar' is a parent of 'foo'.
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Suppose all samples are recorded in 'foo' and 'bar' only. When it's
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recorded with callchains the output will show something like below
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in the usual (self-overhead-only) output of perf report:
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----------------------------------
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Overhead Symbol
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........ .....................
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60.00% foo
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--- foo
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bar
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main
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__libc_start_main
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40.00% bar
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--- bar
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main
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__libc_start_main
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----------------------------------
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When the --children option is enabled, the 'self' overhead values of
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child functions (i.e. 'foo' and 'bar') are added to the parents to
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calculate the 'children' overhead. In this case the report could be
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displayed as:
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-------------------------------------------
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Children Self Symbol
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........ ........ ....................
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100.00% 0.00% __libc_start_main
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--- __libc_start_main
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100.00% 0.00% main
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--- main
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__libc_start_main
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100.00% 40.00% bar
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--- bar
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main
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__libc_start_main
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60.00% 60.00% foo
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--- foo
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bar
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main
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__libc_start_main
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-------------------------------------------
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In the above output, the 'self' overhead of 'foo' (60%) was add to the
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'children' overhead of 'bar', 'main' and '\_\_libc_start_main'.
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Likewise, the 'self' overhead of 'bar' (40%) was added to the
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'children' overhead of 'main' and '\_\_libc_start_main'.
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So '\_\_libc_start_main' and 'main' are shown first since they have
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same (100%) 'children' overhead (even though they have zero 'self'
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overhead) and they are the parents of 'foo' and 'bar'.
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Since v3.16 the 'children' overhead is shown by default and the output
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is sorted by its values. The 'children' overhead is disabled by
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specifying --no-children option on the command line or by adding
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'report.children = false' or 'top.children = false' in the perf config
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file.
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