Messages in this thread | | | Date | Tue, 30 Jun 2009 19:12:49 -0400 | From | Masami Hiramatsu <> | Subject | Re: [PATCH -tip 3/3] kprobes: cleanup: use list instead of hlist for insn_pages |
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Ingo Molnar wrote: > * 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.
Hi Ingo,
Would I might be misunderstood?
struct list_head { struct list_head *next, *prev; };
struct hlist_node { struct hlist_node *next, **pprev; };
Both of list_head and hlist_node are the same size...
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division
e-mail: mhiramat@redhat.com
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