On 9/7/17, Djalal Harouni <tixxdz@xxxxxxxxx> wrote: > Hi Alexey, > > On Thu, Sep 7, 2017 at 4:04 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> > wrote: >> On Wed, Sep 6, 2017 at 2:04 AM, Alexey Dobriyan <adobriyan@xxxxxxxxx> >> wrote: >>> On 9/6/17, Randy Dunlap <rdunlap@xxxxxxxxxxxxx> wrote: >>>> On 09/05/17 15:53, Andrew Morton wrote: > [...] >>>> >>>> also, I expect that the tiny kernel people will want kconfig options >>>> for >>>> these syscalls. >>> >>> We'll add it but the question if it is a good idea. Ideally these system >>> calls >>> should be mandatory and /proc optional. >>> >>> $ size kernel/pidmap.o fs/fdmap.o >>> text data bss dec hex filename >>> 560 0 0 560 230 kernel/pidmap.o >>> 617 0 0 617 269 fs/fdmap.o >> >> After much discussion at LPC/KS last year, I thought the idea was to >> try to speed up /proc rather than replacing it outright. The two >> specific ideas I recall were: >> >> 1. Add a syscall like readfileat() that you can use to, in a single >> operation, open, read, and close a /proc file (or other file). This >> should vastly reduce locking and RCU overhead. >> >> 2. Add a /proc file that has a nice binary format for task info. >> (nl_attr?) >> >> I don't see why pidmap() deserves to be significantly faster than >> getdents(). >> >> Also, a pidmap() syscall like this inherently bypasses any security >> restrictions implied by the way that /proc is mounted. It can respect >> hidepid, but hidepid (as a per-namespace concept) is an enormous turd >> that badly needs to be deprecated, and Djalal is working on exactly >> that. > > Yes as noted by Andy, me and Alexey Gladkov are working on modernizing > procfs [1] and to reduce/remove ties within pid namespaces which has lot > of problems now. > ... Kudos for digging into this mess. But the question will remain: how get pids of existing processes quickly. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
