Thread

1. Inline MemoryContextSwitchTo?

   Tom Lane <tgl@sss.pgh.pa.us> — 2005-02-06T23:05:36Z

   Can anyone think of a reason we aren't inlining MemoryContextSwitchTo()
   in GCC builds, similarly to the way list_head() et al are handled?
   
   It wouldn't be a huge gain, but I consistently see MemoryContextSwitchTo
   eating a percent or three of most profiles.
   
   			regards, tom lane
   
   

2. Re: Inline MemoryContextSwitchTo?

   Karel Zak <zakkr@zf.jcu.cz> — 2005-02-07T08:13:09Z

   On Sun, 2005-02-06 at 18:05 -0500, Tom Lane wrote:
   > Can anyone think of a reason we aren't inlining MemoryContextSwitchTo()
   > in GCC builds, similarly to the way list_head() et al are handled?
   > 
   > It wouldn't be a huge gain, but I consistently see MemoryContextSwitchTo
   > eating a percent or three of most profiles.
   
   Sounds good. 
   
   I think we can inlining all MemoryContext functions which check memory
   context header and call context->metods->...() only. An example
   MemoryContextAlloc() that is very often called from code too.
   
   	Karel
   
   -- 
   Karel Zak <zakkr@zf.jcu.cz>
   
   
   

3. Re: Inline MemoryContextSwitchTo?

   Simon Riggs <simon@2ndquadrant.com> — 2005-02-07T08:28:09Z

   >Karel Zak wrote
   > On Sun, 2005-02-06 at 18:05 -0500, Tom Lane wrote:
   > > Can anyone think of a reason we aren't inlining
   > MemoryContextSwitchTo()
   > > in GCC builds, similarly to the way list_head() et al are handled?
   > >
   > > It wouldn't be a huge gain, but I consistently see
   > MemoryContextSwitchTo
   > > eating a percent or three of most profiles.
   >
   > Sounds good.
   >
   > I think we can inlining all MemoryContext functions which check memory
   > context header and call context->metods->...() only. An example
   > MemoryContextAlloc() that is very often called from code too.
   
   Yes, thats good.
   
   But why MemoryContextSwitchTo ? That seems to come out much lower than
   MemoryContextAllocZeroAligned or MemoryContextAlloc on the profiles I've
   seen.
   
   Best Regards, Simon Riggs
   
   
   

4. Re: Inline MemoryContextSwitchTo?

   Tom Lane <tgl@sss.pgh.pa.us> — 2005-02-07T15:28:25Z

   "Simon Riggs" <simon@2ndquadrant.com> writes:
   > But why MemoryContextSwitchTo ?
   
   Because (a) it's so small that inlining it will probably be a net code
   savings rather than expenditure, and (b) it does have noticeable cost.
   For example, in this gprof profile taken Saturday:
   
     %   cumulative   self              self     total           
    time   seconds   seconds    calls  ms/call  ms/call  name    
    31.25     22.40    22.40                             _mcount
     3.31     24.77     2.37   704032     0.00     0.02  IndexNext
     2.82     26.79     2.02  2112850     0.00     0.00  AllocSetAlloc
     2.48     28.57     1.78  2821112     0.00     0.00  LockBuffer
     2.13     30.10     1.53   701932     0.00     0.01  heap_release_fetch
     1.97     31.51     1.41  6310394     0.00     0.00  MemoryContextSwitchTo
     1.97     32.92     1.41   699632     0.00     0.00  int8inc
     1.66     34.11     1.19  1886388     0.00     0.00  LWLockAcquire
     1.62     35.27     1.16   474244     0.00     0.00  hash_search
     1.56     36.39     1.12  2109900     0.00     0.00  AllocSetReset
     1.46     37.44     1.05   701901     0.00     0.00  _bt_restscan
     1.42     38.46     1.02  2109079     0.00     0.00  memset
     1.39     39.46     1.00   701901     0.00     0.00  _bt_step
     1.24     40.35     0.89   701833     0.00     0.00  ExecEvalExprSwitchContext
     1.20     41.21     0.86   704143     0.00     0.00  _bt_checkkeys
     1.17     42.05     0.84  1886388     0.00     0.00  LWLockRelease
     1.17     42.89     0.84   701901     0.00     0.00  _bt_next
     1.05     43.64     0.75   701833     0.00     0.00  HeapTupleSatisfiesSnapshot
     1.03     44.38     0.74   704144     0.00     0.01  btgettuple
     1.03     45.12     0.74                             $$dyncall
     1.02     45.85     0.73  2110119     0.00     0.00  AllocSetCheck
     0.91     46.50     0.65   706412     0.00     0.01  ReleaseAndReadBuffer
   (all else below 1%)
   
   the only thing I see in that list that looks reasonable to inline is
   MemoryContextSwitchTo.  (This is ye olde test_setup/test_run case on
   a single processor, which is not very interesting lock-wise but I wanted
   to reconfirm that we weren't spending a large fraction of the runtime
   inside bufmgr.)
   
   			regards, tom lane