From: Sergey Ostanevich via Tarantool-patches <tarantool-patches@dev.tarantool.org> To: Sergey Kaplun <skaplun@tarantool.org> Cc: tarantool-patches@dev.tarantool.org Subject: Re: [Tarantool-patches] [PATCH luajit 1/2] Add support for full-range 64 bit lightuserdata. Date: Sun, 1 Aug 2021 19:25:41 +0300 [thread overview] Message-ID: <9C3661B1-0D21-42B7-94F6-C9C14FCEBCCD@tarantool.org> (raw) In-Reply-To: <YQFNrNhjNLAvtQ5M@root> [-- Attachment #1: Type: text/plain, Size: 3655 bytes --] Hi! Thanks for the patch! Some minor message fixes, one great gag from Mike’s code and a test request. Regards, Sergos > > The new commit message is the following: > > =================================================================== > Add support for full-range 64 bit lightuserdata. > > (cherry picked from commit e9af1abec542e6f9851ff2368e7f196b6382a44c) > > LuaJIT uses special NaN-tagging technique to store internal type on > the Lua stack. In case LJ_GC64 first 13 bits are set in special NaN ^^^^^^^ ^ In case of the > type (0xfff8...). FPU generates the only one type. The next 4 bits are ^^^^^^^^^^^ Which one and how is it relevant? > used for an internal LuaJIT type of object on stack. The next 47 bits > are used for storing this object's content. For userdata, it is its > address. In case arm64 the pointer can have more than 47 significant ^^^^^ For > bits [1]. In this case the error BADLU error is raised. > > For the support of full 64-bit range lightuserdata pointers two new > fields in GCState are added: > > `lightudseg` - vector of segments of lightuserdata. Each element keeps > 32-bit value. 25 MSB equal to MSB of lightuserdata address, the rest are ^ 64bit > filled with zeros. The length of the vector is power of 2. > > `lightudnum` - the length - 1 of aforementioned vector (up to 255). > > When lightuserdata is pushed on the stack, if its segment is not stored > in vector new value is appended on top of this vector. The maximum ^^^^^^^^^ to At first I want you to put it as ’not found’ instead of ’not stored’. Then I start thinking over ‘on top’ for a vector and I got a strange feeling... Now tell me, every time you put a LUD pointer to stack you have to roll over all present segments in this '>>>' plain loop below? --- a/src/lj_api.c +++ b/src/lj_api.c +#if LJ_64 +static void *lightud_intern(lua_State *L, void *p) +{ + global_State *g = G(L); + uint64_t u = (uint64_t)p; + uint32_t up = lightudup(u); + uint32_t *segmap = mref(g->gc.lightudseg, uint32_t); + MSize segnum = g->gc.lightudnum; + if (segmap) { + MSize seg; >>> + for (seg = 0; seg <= segnum; seg++) >>> + if (segmap[seg] == up) /* Fast path. */ >>> + return (void *)(((uint64_t)seg << LJ_LIGHTUD_BITS_LO) | lightudlo(u)); + segnum++; + } + if (!((segnum-1) & segnum) && segnum != 1) { + if (segnum >= (1 << LJ_LIGHTUD_BITS_SEG)) lj_err_msg(L, LJ_ERR_BADLU); + lj_mem_reallocvec(L, segmap, segnum, segnum ? 2*segnum : 2u, uint32_t); + setmref(g->gc.lightudseg, segmap); + } + g->gc.lightudnum = segnum; + segmap[segnum] = up; + return (void *)(((uint64_t)segnum << LJ_LIGHTUD_BITS_LO) | lightudlo(u)); +} +#endif + Can’t help to laugh at Mike’s /* Fast path */, brilliant isn’t it? Perhaps addition of a new segment is not so often - and is counted to 256 - so we can easily sort the array each time to make it log(n) rather (n) for each lua_pushlightuserdata()? > <snipped> > > See the iterative patch below. > > =================================================================== > diff --git a/test/tarantool-tests/lj-49-bad-lightuserdata.test.lua b/test/tarantool-tests/lj-49-bad-lightuserdata.test.lua This one tests the LUD push/pop to/fro stack. How about those > all internal usage of lightuserdata (for hooks, > profilers, built-in package, IR and so on) is changed to special values > on Lua Stack. Can you add at least _some_ test to verify memprof is fine? [-- Attachment #2: Type: text/html, Size: 29264 bytes --]
next prev parent reply other threads:[~2021-08-01 16:25 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-06 17:40 [Tarantool-patches] [PATCH luajit 0/2] arm64: fix 48-bit addresses issues Sergey Kaplun via Tarantool-patches 2021-07-06 17:40 ` [Tarantool-patches] [PATCH luajit 1/2] Add support for full-range 64 bit lightuserdata Sergey Kaplun via Tarantool-patches 2021-07-27 13:59 ` Igor Munkin via Tarantool-patches 2021-07-28 12:29 ` Sergey Kaplun via Tarantool-patches 2021-08-01 10:36 ` Igor Munkin via Tarantool-patches 2021-08-02 14:56 ` Sergey Kaplun via Tarantool-patches 2021-08-01 16:25 ` Sergey Ostanevich via Tarantool-patches [this message] 2021-08-02 14:51 ` Sergey Kaplun via Tarantool-patches 2021-08-02 15:42 ` Igor Munkin via Tarantool-patches 2021-08-10 16:46 ` Sergey Ostanevich via Tarantool-patches 2021-08-11 5:54 ` Vitaliia Ioffe via Tarantool-patches 2021-07-06 17:40 ` [Tarantool-patches] [PATCH luajit 2/2] Linux/ARM64: Make mremap() non-moving due to VA space woes Sergey Kaplun via Tarantool-patches 2021-07-27 15:23 ` Igor Munkin via Tarantool-patches 2021-07-28 12:29 ` Sergey Kaplun via Tarantool-patches 2021-08-01 10:36 ` Igor Munkin via Tarantool-patches 2021-08-01 16:59 ` Sergey Ostanevich via Tarantool-patches 2021-08-02 15:08 ` Sergey Kaplun via Tarantool-patches 2021-08-02 15:55 ` Sergey Ostanevich via Tarantool-patches 2021-08-02 15:11 ` Sergey Kaplun via Tarantool-patches 2021-08-11 7:21 ` [Tarantool-patches] [PATCH luajit 0/2] arm64: fix 48-bit addresses issues Igor Munkin via Tarantool-patches
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