On Tue, Feb 07, 2023 at 05:14:54PM +0000, Alan Maguire wrote: SNIP > > Changes since v2 [2] > - Arnaldo incorporated some of the suggestions in the v2 thread; > these patches are based on those; the relevant changes are > noted as committer changes. > - Patch 1 is unchanged from v2, but the rest of the patches > have been updated: > - Patch 2 separates out the changes to the struct btf_encoder > that better support later addition of functions. > - Patch 3 then is changed insofar as these changes are no > longer needed for the function addition refactoring. > - Patch 4 has a small change; we need to verify that an > encoder has actually been added to the encoders list > prior to removal > - Patch 5 changed significantly; when attempting to measure > performance the relatively good numbers attained when using > delayed function addition were not reproducible. > Further analysis revealed that the large number of lookups > caused by the presence of the separate function tree was > a major cause of performance degradation in the multi > threaded case. So instead of maintaining a separate tree, > we use the ELF function list which we already need to look > up to match ELF -> DWARF function descriptions to store > the function representation. This has 2 benefits; firstly > as mentioned, we already look up the ELF function so no > additional lookup is required to save the function. > Secondly, the ELF representation is identical for each > encoder, so we can index the same function across multiple > encoder function arrays - this greatly speeds up the > processing of comparing function representations across > encoders. There is still a performance cost in this awesome.. great we can do it without the extra tree I wonder we could save some cycles just by memdup-ing the encoder->functions array for the subsequent encoders, but that's ok for another patch ;-) thanks, jirka
