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charset=us-ascii Content-Disposition: inline In-Reply-To: <171131951305.13576.14679515391685379475@noble.neil.brown.name> X-Rspamd-Queue-Id: 936CA8000E X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: zgb5513o41beno78am5odp87egz7i7y5 X-HE-Tag: 1711356196-259557 X-HE-Meta: U2FsdGVkX1/x6b0AtquQMahvMpvKt14I5/CjMQl+OiNlSs8jwS2n65pPuOwEdQme3PDYeVizVT2O6M7oL6SFkKwFftmGmbMUjRL+rUNMCc6ZixwSoss8E/cX54WBHCkNrV0O3a+cQf1Qap1QFwK/dba2ra2lfSXKtz6dVkJTj5WQcwJU29YRo5B+9P2WqLckxlyR+Q/Nf48k74EynOyaQyAaCNavq8zA69rbfMN2ZH782d0qIMoT3qxwq2Zye5c48PFRwqBx+ECjqnHRrTwn6ryA73sRwboKb4w9Y4+oLhpltX2aGXhBCRik5BNU6bR04APDLjPEKfpindxqnZqXX1U9Z/WHVmDhK43wdT6TyNqhDvn35iWkvEKAXXArbHkS0EeeakKc+XLtNCiSqsNk96Lr5ekeWJ8Nb8TWDty2j5x+ynVcqXCxqv+ge/oQdVMV/ME5GgkfJkaFTxa0GIJ7QXv3pQpgwwK6dycGgj+rDXvviPP4X32q4L+plJSGZmnOVA997JjJz8B2fif9lqGrxCMg+d0mAskPSAomTOTc554xqL9X4Lk15pvkoqbXQ/d0gW0AEiYc3g2buB8m6rEZT7OqZywBXv4tEPPc/Iy+s+3hytJPpRpMhs2B1cx3IHYXmSBQ90JIZG5JeX6VqlBn70wD3l36tPQ49wjIRyE8XBifHMTKWPcO8DeBubTTC+8+zcPngOmP0y/f1siLNEoiOVh2iKtWeWwhzmqPihofWAOAu+lBoGqrai1TEiGYF49jAxByiPidOoZ/vzN8lvURv+t3sDT1XIA8bCEmBEjuAIoCq791fPrdAhL6vhKX2UQfnN9OLFRjHMCYUm6fTg6dWiFjKcokdBzHiBaHaEEVrIStd9bamCY65067PCJ/TyrKiEvaRK09zhS5Fbywtu8kUP3PYgYDPaPtmO6uYfcsnDOznRv7WjcUv/hYnFNWKOA9GQdDgQ/4mc31iCO3AXD eygB1Ccy mSoaaxzEYhV5dAkjMRQgZg6Hua+T0GsNQB8oh0nWqfqa8ZhDFuUMwATa0iZRkS+cVjO6NtS0f2nRqjRpW16dun7DzeCXP+GmhP73qYeQeel+Io5EzpLtlWg4+/ACa/+cLXhoNiiN086UmE0blyF6hygxttQ29uGqk0zmwNmf3Alw33mZqEkej6Mbv3SkutMteny5Mq0xxUqxzT3eSAY7v6qRcqoXDrS+ELh1H2EUR2L4m858WdegtiRAWt8Im03DE+SDvm94KIVIEXQGHGRWfdlhobCxJyaYY4t+az8VYADz7qay8pT/grbJHGw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000016, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 25, 2024 at 09:31:53AM +1100, NeilBrown wrote: > On Fri, 22 Mar 2024, Dan Carpenter wrote: > > On Fri, Mar 22, 2024 at 12:47:42PM +1100, NeilBrown wrote: > > > On Thu, 21 Mar 2024, Dan Carpenter wrote: > > > > On Mon, Mar 04, 2024 at 09:45:48AM +1100, NeilBrown wrote: > > > > > I have in mind a more explicit statement of how much waiting is > > > > > acceptable. > > > > > > > > > > GFP_NOFAIL - wait indefinitely > > > > > > > > Why not call it GFP_SMALL? It wouldn't fail. The size would have to be > > > > less than some limit. If the size was too large, that would trigger a > > > > WARN_ON_ONCE(). > > > > > > I would be happy with GFP_SMALL. It would never return NULL but might > > > block indefinitely. It would (as you say) WARN (maybe ONCE) if the size > > > was considered "COSTLY" and would possibly BUG if the size exceeded > > > KMALLOC_MAX_SIZE. > > > > I'd like to keep GFP_SMALL much smaller than KMALLOC_MAX_SIZE. IIf > > you're allocating larger than that, you'd still be able to GFP_NOFAIL. > > I looked quickly an I think over 60% of allocations are just sizeof(*p) > > and probably 90% are under 4k. > > What do you mean exactly by "keep"?? Poor word choice... > Do you mean WARN_ON if it is "too big" - certainly agree. > Do you mean BUG_ON if it is "too big" - maybe agree. WARN_ON_ONCE(). But a lot of people have reboot on Oops enabled so triggering a WARN_ON() is still a very serious bug. > Do you mean return NULL if it is "too big" - definitely disagree. Yeah. It's going to be a style violation to check a GFP_SMALL allocation for NULL so it needs to have GFP_NOFAIL behavior. It can still fail if it's larger than KMALLOC_MAX_SIZE. > Do you mean build failure if it could be too big - I would LOVE that, > but I don't think we can do that with current build tools. The limit is going to be a constant so using static analysis to check that is easier than checking if we're less than some variable. regards, dan carpenter