On Thu, 2007-05-24 at 11:50 -0700, Andrew Morton wrote: > On Thu, 24 May 2007 18:15:17 +0100 > Michael-Luke Jones <[EMAIL PROTECTED]> wrote: > > > Attached is a patch which may be desirable for -mm. It applies > > directly to 2.6.22-rc2-mm1. > > > > The patch removes the 'unsafe' LZO decompression function, lowering > > the size of the minilzo.c file by nearly 500 out of an original 1727 > > lines. It also removes references to the 'unsafe' decompression > > function in the public LZO header and the EXPORT_SYMBOL_GPL declaration. [...] > > Comments / disagreement all welcome :) > > This is obviously a highly desirable thing to do for a number of reasons. > But have we quantified the performance difference?
Ok, I've done some tests: 1. Comparing the safe and unsafe functions For my minilzo kernel patch, the safe version showed a 7.2% performance hit. For Nitin's patch, it showed a 3.2% performance hit (but see below). Could be a lot worse and I don't object to the removal of the unsafe version. 2. Comparing Nitin's code with my minilzo based kernel patch. My kernel patch is about 2.25 times faster at decompression (16725Kb/ms vs 7399Kb/ms) and fractionally faster at compression (1434kb/ms vs 1490kb/ms). As things stand the performance of Nitin's patch is therefore unacceptable as that is a significant decompression performance loss. These tests are on 32 bit Intel and in userspace but I've found them to be a pretty good indicator of what happens in the real world and on other architectures. For simplicity I made these tests with some existing code I had around but its licence is such I can't share it, much to my frustration. Cheers, Richard - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
