[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 5/9] xen: introduce assign_pages_nr
On 01.07.2021 11:24, Julien Grall wrote: > On 01/07/2021 09:26, Jan Beulich wrote: >> On 30.06.2021 20:29, Julien Grall wrote: >>> On 10/06/2021 10:49, Jan Beulich wrote: >>>> On 07.06.2021 04:43, Penny Zheng wrote: >>>>> Introduce new interface assign_pages_nr to deal with when page number is >>>>> not in a power-of-two, which will save the trouble each time user needs >>>>> to split the size in a power of 2 to use assign_pages. >>>> >>>> First of all I still don't see why in this one special case it is a >>>> meaningful burden to do the count-to-order conversion in the caller you >>>> mean to add, >>> >>> This sort of works for one caller. However, I would expect some more >>> user in the future (we use it for Live-Update). >>> >>>> and hence why we really need this new function (to keep it >>>> simple, you could even have the caller not break down to arbitrary >>>> power-of-2 chunks, but simply iterate over all individual [order-0] >>>> pages). >>> >>> The function assign_pages() will always use 1U << order (and sadly 1 << >>> order). So we would end up to convert the count in multiple order for >>> then directly converting back to a number. To me, this sounds rather >>> pointless... >>> >>> There are also a slight benefits to call assign_pages() a single time >>> during boot because it will reduce the number of time we need to >>> lock/unlock d->page_alloc_lock. >> >> Well, all of this is why I did add ... >> >>>> The more that I'm not happy with the chosen name, despite it >>>> having been suggested during v1 review. _If_ we needed two functions, >>>> imo they ought to be named assign_page() (dealing with a single page of >>>> the given order) and assign_pages(). Backporting confusion could be >>>> helped by altering the order of parameters, such that the compiler >>>> would point out that adjustments at call sites are needed. >> >> ... this. > > Oh, it wasn't entirely clear whether you were objecting of offering the > possibility to pass a number of pages rather than an order. Easily understood: I indeed we trying to express my preference to stick to what we have, but trying to suggest a variant that I think I could live with. Jan
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