Re: Disk IO performance

Daniel Molina Wegener wrote: > On Sunday 28 November 2010, > Larry Garfield <larry@garfieldtech.com> wrote: > >> There are many things that everybody "knows" about optimizing PHP >> code. One of them is that one of the most expensive parts of the >> process is loading code off of disk and compiling it, which is why >> opcode caches >> are such a bit performance boost. The corollary to that, of course, >> is that more files = more IO and therefore more of a performance hit. > > It depends on the implementation that PHP uses to open the file. For > example on Linux and similar operating systems, PHP uses the mmap(2) > function instead of read(2) or fread(2) functions, so it maps the > complete file into memory, that is more faster than using partial file > reads. I doubt if a read(file,1Mb) and an mmap(file,1Mb) will be very different. The file has got to be hauled in from disk regardless of which function you choose. -- Per Jessen, Zürich (2.6°C)