On Thu, Nov 06, 2014 at 05:32:00PM -0500, Rik van Riel wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 11/03/2014 03:42 PM, j.glisse@xxxxxxxxx wrote: > > From: Jérôme Glisse <jglisse@xxxxxxxxxx> > > > > Page table is a common structure format most notably use by cpu > > mmu. The arch depend page table code has strong tie to the > > architecture which makes it unsuitable to be use by other non arch > > specific code. > > > > This patch implement a generic and arch independent page table. It > > is generic in the sense that entry size can be u64 or unsigned long > > (or u32 too on 32bits arch). > > > > It is lockless in the sense that at any point in time you can have > > concurrent thread updating the page table (removing or changing > > entry) and faulting in the page table (adding new entry). This is > > achieve by enforcing each updater and each faulter to take a range > > lock. There is no exclusion on range lock, ie several thread can > > fault or update the same range concurrently and it is the > > responsability of the user to synchronize update to the page table > > entry (pte), update to the page table directory (pdp) is under gpt > > responsability. > > > > API usage pattern is : gpt_init() > > > > gpt_lock_update(lock_range) // User can update pte for instance by > > using atomic bit operation // allowing complete lockless update. > > gpt_unlock_update(lock_range) > > > > gpt_lock_fault(lock_range) // User can fault in pte but he is > > responsible for avoiding thread // to concurrently fault the same > > pte and for properly accounting // the number of pte faulted in the > > pdp structure. gpt_unlock_fault(lock_range) // The new faulted pte > > will only be visible to others updaters only // once all concurrent > > faulter on the address unlock. > > > > Details on how the lockless concurrent updater and faulter works is > > provided in the header file. > > > > Changed since v1: - Switch to macro implementation instead of using > > arithmetic to accomodate the various size for table entry > > (uint64_t, unsigned long, ...). This is somewhat less flexbile but > > right now there is no use for the extra flexibility v1 was > > offering. > > > > Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx> > > Never a fan of preprocessor magic, but I see why it's needed. > > Acked-by: Rik van Riel <riel@xxxxxxxxxx> v1 is not using preprocessor but has a bigger gpt struct footprint and also more complex calculation for page table walking due to the fact that i just rely more on runtime computation than on compile time shift define through preprocessor magic. Given i am not a fan either of preprocessor magic if it makes you feel any better i can resort to use v1, both have seen same kind of testing and both are functionaly equivalent (API they expose is obviously slightly different). I am not convince that what the computation i save using preprocessor will show up in anyway as being bottleneck for hot path. Cheers, Jérôme > > > - -- > All rights reversed > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 > > iQEcBAEBAgAGBQJUW/bgAAoJEM553pKExN6Dl6IH/i9rSRtvdO9+lf1cUe686XJb > GZ8KOp3Qa+ac0W63NqEaY5W+Fi7qyZJdoRFLCyOHBSP44qg9yoEJz8IbdPVNRjGG > lXyyfyOP0PY3wSakSP/IS3OIvapav6YPXiOIX7FlzPTReL+RWJPDYpmvi6S6nXgS > PuVTedVT5yaZwcqh0CyfDZ8pQqxEBSyvdVY/ntia7hxtUk9Or/sWVaRn8RE1u6EZ > xA5DtjqTB+UHmNtmTNe2B5i2TmvhIFYr+/ydCs76osR2e+UBcqQtnN3cdudZWyj3 > Pk1c/7qtTqgS2pdiIkpjCKH5qXIszGM6vDSGCjM/4/7afX+vjk7UQDWeXGfzQFs= > =ndqX > -----END PGP SIGNATURE----- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>