Messages in this thread | | | Date | Tue, 30 Jun 2009 23:50:23 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH -tip 3/3] kprobes: cleanup: use list instead of hlist for insn_pages |
| |
* Masami Hiramatsu <mhiramat@redhat.com> wrote:
> Ingo Molnar wrote: > > * Masami Hiramatsu <mhiramat@redhat.com> wrote: > > > >> Use struct list instead of struct hlist for managing insn_pages, > >> because insn_pages doesn't use hash table. > > > >> struct kprobe_insn_page { > >> - struct hlist_node hlist; > >> + struct list_head list; > > > > Hm, you know that this increases the size of kprobe_insn_page by 4/8 > > bytes, right? > > Sure, that will increase size. > > > hlists are not just used for hashes - but also when we want a more > > compact / smaller list head. > > Oh, I thought hlists are used for hash tables...
... because they are smaller, hence the hash table of list heads becomes twice as dense as with list_head.
But otherwise it's an (almost) equivalent primitive to list_head, with a slightly higher runtime cost versus better RAM footprint.
> > How many kprobe_insn_page's can be allocated in the system, > > maximally? > > It's depends on how many probes you will use, but logically, 1 > kprobe_insn_pages is allocated per 4096/16 = 256 probes. So, if > you use 25,600 probes on your system, memory consumption will > increase 400/800 bytes.
it's your call really - just wanted to react on the 'because it should be used for hash tables' comment in the changelog.
Ingo
| |